The disappearance of a Malaysia Airlines flight more than a week ago was an "intentional, deliberate act" that may have originated in the cockpit, the chairman of the House Homeland Security Committee said Sunday. 
 
 The vanishing of the aircraft "was not an accident. It was an intentional, deliberate act to bring down this airplane," Rep. Mike McCaul (R-Texas) said on "Fox News Sunday." 
 
 His remarks followed statements from the Malaysian prime minister over the weekend that the movements of the plane appeared "deliberate." 
 
 While terrorism cannot be ruled out, McCaul said his briefings with top administration intelligence officials indicate that one of the pilots may have been behind the disappearance of the plane and the 239 people aboard. 
 
 “Something was going on with the pilot. This all leads toward the cockpit,” McCaul said. 
 
 Peter Goelz, a former managing director at the National Transportation Safety Board, agreed, particularly given that communications equipment on the plane appears to have been turned off by people aboard the aircraft with a significant amount of training. 
 
 “That is damning evidence that indicates something was going on in the flight deck,” Goelz said. 
 
 Read more about: Malaysia, Mike McCaul, Flight 370 ||||| Story highlights Official: Programmed change in direction occurred 12 minutes before sign off 
 
 Analyst: "Sometimes an erratic flight path is heroism, not terrorism" 
 
 Law enforcement official: Plane's turn almost certainly programmed from cockpit 
 
 Officials say nothing on pilots' computers, e-mails indicates deviation was planned 
 
 New information from the Thai government bolsters the belief that missing Malaysia Airlines Flight 370 took a sharp westward turn after communication was lost. 
 
 And it looks like that turn was no accident. 
 
 A law enforcement official told CNN Tuesday that the aircraft's first turn to the west was almost certainly programmed by somebody in the cockpit. 
 
 The official, who has been briefed on the investigation, said the programmed change in direction was entered at least 12 minutes before the plane's co-pilot signed off to air traffic controllers, telling them, "All right, good night." 
 
 Analysts on CNN's "AC360" offered different interpretations of what that could mean -- with some experts cautioning the change in direction could have been part of an alternate flight plan programmed in advance in case of emergency, and others warning it could show something more nefarious was afoot. 
 
 "We don't know when specifically it was entered," said Mary Schiavo, a CNN aviation analyst and former inspector general for the U.S. Department of Transportation. 
 
 New York Times reporter Michael Schmidt said the new timeframe "makes the issue of foul play seem more significant." 
 
 "Because by doing that," he said, "what it basically shows is that this thing was already heading in a different direction when they're saying good night." 
 
 But still, the new details about what happened don't add up to a clear answer. 
 
 "Like everything on this story, we learn a little bit," Schmidt said, "but then we just have more questions." 
 
 Evidence that someone programmed the plane's computer and the Thai data that surfaced Tuesday corroborate a leading theory from Malaysian investigators: The missing plane veered off course in a deliberate act by someone who knew what they were doing. 
 
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 40 photos: The search for MH370 40 photos: The search for MH370 Police carry a piece of debris on Reunion Island, a French territory in the Indian Ocean, on Wednesday, July 29. A week later, authorities confirmed that the debris was from Malaysia Airlines Flight 370, which disappeared on March 8, 2014. Hide Caption 1 of 40 40 photos: The search for MH370 Relatives of the flight's passengers console each other outside the Malaysia Airlines office in Subang, Malaysia, on Thursday, February 12. Protesters had demanded that the airline withdraw the statement made in January that all the passengers aboard the plane were dead. Hide Caption 2 of 40 40 photos: The search for MH370 A police officer watches a crying couple cry outside the airline's office building in Beijing after officials refused to meet with them on June 11, 2014. The couple's son was on the plane. Hide Caption 3 of 40 40 photos: The search for MH370 Members of the media scramble to speak with Azharuddin Abdul Rahman, director general of Malaysia's Civil Aviation Department, at a hotel in Kuala Lumpur, Malaysia, on May 27, 2014. Data from communications between satellites and the missing flight was released the day before, more than two months after relatives of passengers said they requested it be made public. Hide Caption 4 of 40 40 photos: The search for MH370 Operators aboard the Australian ship Ocean Shield move Bluefin-21, the U.S. Navy's autonomous underwater vehicle, into position to search for the jet on April 14, 2014. Hide Caption 5 of 40 40 photos: The search for MH370 A member of the Royal New Zealand Air Force looks out of a window while searching for debris off the coast of western Australia on April 13, 2014. Hide Caption 6 of 40 40 photos: The search for MH370 The HMS Echo, a vessel with the British Roya; Navy, moves through the waters of the southern Indian Ocean on April 12, 2014. Hide Caption 7 of 40 40 photos: The search for MH370 A Royal Australian Air Force AP-3C Orion, on a mission to drop sonar buoys to assist in the search, flies past the Australian vessel Ocean Shield on April 9, 2014. Hide Caption 8 of 40 40 photos: The search for MH370 A relative of a missing passenger cries at a vigil in Beijing on April 8, 2014. Hide Caption 9 of 40 40 photos: The search for MH370 Australian Defense Force divers scan the water for debris in the southern Indian Ocean on April 7, 2014. Hide Caption 10 of 40 40 photos: The search for MH370 A towed pinger locator is readied to be deployed off the deck of the Australian vessel Ocean Shield on April 7, 2014. Hide Caption 11 of 40 40 photos: The search for MH370 A member of the Royal New Zealand Air Force looks at a flare in the Indian Ocean during search operations on April 4, 2014. Hide Caption 12 of 40 40 photos: The search for MH370 On March 30, 2014, a woman in Kuala Lumpur prepares for an event in honor of those aboard Flight 370. Hide Caption 13 of 40 40 photos: The search for MH370 The sole representative for the families of Flight 370 passengers leaves a conference at a Beijing hotel on March 28, 2014, after other relatives left en masse to protest the Malaysian government's response to their questions. Hide Caption 14 of 40 40 photos: The search for MH370 A member of the Royal Australian Air Force is silhouetted against the southern Indian Ocean during the search for the missing jet on March 27, 2014. Hide Caption 15 of 40 40 photos: The search for MH370 Flight Lt. Jayson Nichols looks at a map aboard a Royal Australian Air Force aircraft during a search on March 27, 2014. Hide Caption 16 of 40 40 photos: The search for MH370 People in Kuala Lumpur light candles during a ceremony held for the missing flight's passengers on March 27, 2014. Hide Caption 17 of 40 40 photos: The search for MH370 Malaysian Prime Minister Najib Razak, center, delivers a statement about the flight on March 24, 2014. Razak's announcement came after the airline sent a text message to relatives saying it "deeply regrets that we have to assume beyond any reasonable doubt that MH 370 has been lost and that none of those onboard survived." Hide Caption 18 of 40 40 photos: The search for MH370 Grieving relatives of missing passengers leave a hotel in Beijing on March 24, 2014. Hide Caption 19 of 40 40 photos: The search for MH370 A passenger views a weather map in the departures terminal of Kuala Lumpur International Airport on March 22, 2014. Hide Caption 20 of 40 40 photos: The search for MH370 A Chinese satellite captured this image, released on March 22, 2014, of a floating object in the Indian Ocean, according to China's State Administration of Science. It was a possible lead in the search for the missing plane. Surveillance planes were looking for two objects spotted by satellite imagery in remote, treacherous waters more than 1,400 miles from the west coast of Australia. Hide Caption 21 of 40 40 photos: The search for MH370 Satellite imagery provided by the Australian Maritime Safety Authority on March 20, 2014, showed debris in the southern Indian Ocean that could have been from Flight 370. The announcement by Australian officials raised hopes of a breakthrough in the frustrating search. Hide Caption 22 of 40 40 photos: The search for MH370 Another satellite shot provided by the Australian Maritime Safety Authority shows possible debris from the flight. Hide Caption 23 of 40 40 photos: The search for MH370 A distraught relative of a missing passenger breaks down while talking to reporters at Kuala Lumpur International Airport on March 19, 2014. Hide Caption 24 of 40 40 photos: The search for MH370 On March 18, 2014, a relative of a missing passenger tells reporters in Beijing about a hunger strike to protest authorities' handling of information about the missing jet. Hide Caption 25 of 40 40 photos: The search for MH370 U.S. Navy crew members assist in search-and-rescue operations in the Indian Ocean on March 16, 2014. Hide Caption 26 of 40 40 photos: The search for MH370 Members of the Chinese navy continue search operations on March 13, 2014. After starting in the sea between Malaysia and Vietnam, the plane's last confirmed location, search efforts expanded west into the Indian Ocean. Hide Caption 27 of 40 40 photos: The search for MH370 A Vietnamese military official looks out an aircraft window during search operations March 13, 2014. Hide Caption 28 of 40 40 photos: The search for MH370 Malaysian air force members look for debris near Kuala Lumpur on March 13, 2014. Hide Caption 29 of 40 40 photos: The search for MH370 Relatives of missing passengers wait for the latest news at a hotel in Beijing on March 12, 2014. Hide Caption 30 of 40 40 photos: The search for MH370 A member of the Vietnamese air force checks a map while searching for the missing plane on March 11, 2014. Hide Caption 31 of 40 40 photos: The search for MH370 A Vietnamese air force plane found traces of oil that authorities had suspected to be from the missing Malaysia Airlines plane, the Vietnamese government online newspaper reported on March 8, 2014. However, a sample from the slick showed it was bunker oil, typically used to power large cargo ships, Malaysia's state news agency, Bernama, reported on March 10, 2014. Hide Caption 32 of 40 40 photos: The search for MH370 A U.S. Navy Seahawk helicopter lands aboard the USS Pinckney to change crews on March 9, 2014, before returning to search for the missing plane in the Gulf of Thailand. Hide Caption 33 of 40 40 photos: The search for MH370 Buddhist monks at Kuala Lumpur International Airport offer a special prayer for the missing passengers on March 9, 2014. Hide Caption 34 of 40 40 photos: The search for MH370 Members of a Chinese emergency response team board a rescue vessel at the port of Sanya in China's Hainan province on March 9, 2014. Hide Caption 35 of 40 40 photos: The search for MH370 The rescue vessel sets out from Sanya in the South China Sea on March 9, 2014. Hide Caption 36 of 40 40 photos: The search for MH370 Malaysian Prime Minister Najib Razak, center, arrives to meet family members of missing passengers at the reception center at Kuala Lumpur International Airport on March 8, 2014. Hide Caption 37 of 40 40 photos: The search for MH370 A relative of two missing passengers reacts at their home in Kuala Lumpur on March 8, 2014. Hide Caption 38 of 40 40 photos: The search for MH370 Chinese police at the Beijing airport stand beside the arrival board showing delayed Flight 370 in red on March 8, 2014. Hide Caption 39 of 40 40 photos: The search for MH370 Malaysia Airlines Group CEO Ahmad Juahari Yahya, front, speaks during a news conference at a hotel in Sepang on March 8, 2014. "We deeply regret that we have lost all contacts" with the jet, he said. Hide Caption 40 of 40 
 
 But investigators still don't know who was at the controls, or why whoever was flying the plane apparently took it far from its original destination. 
 
 An initial search of the pilots' personal computers and e-mails found nothing to indicate that the sudden deviation in the aircraft's route was planned, U.S. officials said Tuesday after being briefed by Malaysian authorities. 
 
 The officials said they had also reviewed cockpit conversations between the plane and air traffic controllers and heard nothing suspicious or anything that would explain why the jetliner changed course. 
 
 And a flight simulator belonging to pilot Zaharie Ahmad Shah did not show any of the unexplained paths the plane may have flown after it went off the grid, officials said. 
 
 Schiavo said it's no surprise investigators found nothing suspicious in the pilots' homes. 
 
 "I've worked on many cases were the pilots were suspect, and it turned out to be a mechanical and horrible problem," she said. "And I have a saying myself: Sometimes an erratic flight path is heroism, not terrorism. And I always remind myself of that, not to jump to that conclusion. Sometimes pilots are fighting amazing battles, and we never hear about it. " 
 
 Thailand: Plane sent intermittent signal 
 
 The Thai military's revelation that it also spotted the plane turning west toward the Strait of Malacca is one encouraging sign that investigators could be on the right track after days of searching for the missing plane have failed to turn up any answers about its location. 
 
 The Thai military was receiving normal flight path and communication data from the Boeing 777-200 on its planned March 8 route from Kuala Lumpur to Beijing until 1:22 a.m., when it disappeared from its radar. 
 
 Six minutes later, the Thai military detected an unknown signal, a Royal Thai Air Force spokesman told CNN. This unknown aircraft, possibly Flight 370, was heading the opposite direction. 
 
 Malaysia says the evidence suggests that the plane was deliberately flown off-course, turning west and traveling back over the Malay Peninsula and out into the Indian Ocean. 
 
 The Thai data are the second radar evidence that the plane did indeed turn around toward the Strait of Malacca. 
 
 It follows information from the Malaysian air force that its military radar tracked the plane as it passed over the small island of Pulau Perak in the Strait of Malacca. 
 
 "The unknown aircraft's signal was sending out intermittently, on and off and on and off," the spokesman said. The Thai military lost the unknown aircraft's signal because of the limits of its military radar, he said. 
 
 Investigators say they're still not sure where the plane ended up. 
 
 The latest findings say the plane's last known location detected by a satellite is along two wide arcs: one stretching north over Asia and the other south into the Indian Ocean. The plane's last electronic connection with the satellite was about six hours after it last showed up on Malaysian military radar. 
 
 The total area now being searched stands at 2.97 million square miles -- an area nearly the size of the continental United States -- Hishammuddin Hussein, the Malaysian defense and transport minister said. 
 
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 "This is an enormous search area," Hishammuddin said. "And it is something that Malaysia cannot possibly search on its own. I am therefore very pleased that so many countries have come forward to offer assistance and support to the search and rescue operation." 
 
 Turn made by computer? 
 
 The pilot and first officer of the missing plane, both of them Malaysian, have come under particular scrutiny in the search for clues. 
 
 But officials have reported no evidence to tie the pilot and first officer to the plane's disappearance. 
 
 One aviation expert, writing an opinion piece for CNN.com, floated the idea last week that whoever changed the plane's course was an expert. 
 
 The cockpit computer programming analysis, first reported by The New York Times Tuesday, has increased investigators' focus on the pilot and first officer, the newspaper said. 
 
 Asked about the report Tuesday, Malaysia Airlines Chief Executive Ahmad Jauhari Yahya said, "As far as we're concerned, the aircraft was programmed to fly to Beijing. That's the standard procedure." 
 
 But he didn't rule out the possibility the flight path had been reprogrammed. 
 
 "Once you're in the aircraft," he said, "anything is possible." 
 
 China clears citizens 
 
 China says it has found no evidence that any of its citizens on board the missing plane were involved in hijacking or terrorism. 
 
 Background checks on all passengers from the Chinese mainland on the plane have found nothing to support such suspicions, Huang Huikang, the Chinese ambassador to Malaysia, said Tuesday, according to the state-run Chinese news agency Xinhua. 
 
 Authorities have said they are investigating all 239 people who were on board the flight, which disappeared more than 10 days ago. 
 
 According to the airline, 153 of the 227 passengers on board the plane came from mainland China or Hong Kong. 
 
 By effectively ruling out suspicions for a large majority of the passengers, Chinese authorities appear to have significantly shortened the list of possible suspects in the investigation. 
 
 The Chinese ambassador's statement is also likely to greatly dampen speculation that Uyghur separatists from China's far western region of Xinjiang might have been involved in the plane's disappearance. 
 
 One of the two long corridors where authorities say the plane was last detected stretched over Xinjiang, and unconfirmed reports had suggested the possibility that Uyghurs might be connected to the case. 
 
 Chinese authorities have accused separatists from Xinjiang of carrying out a terrorist attack this month in which eight attackers armed with long knives stormed a train station in Kunming, a city in southwestern China, killing 29 people and wounding more than 140. 
 
 China said Tuesday that it had begun to search for the plane in the parts of its territory that fall under the northern corridor, deploying satellite and radar resources. 
 
 Experts are analyzing past and present data along the arc stretching through Chinese territory, Hong Lei, a Foreign Ministry spokesman, said at a news briefing Tuesday in Beijing. 
 
 Still a mystery 
 
 Eleven days after Flight 370 disappeared, the bottom line is that the fate of the flight remains a mystery. As time has passed, initial theories about mechanical error have led to more elaborate ideas about complicated hijacking or commandeering plots. 
 
 Former Malaysia Airlines pilot Nik Huzlan has flown the same aircraft that is now missing. 
 
 "I know, I flew this plane," he said. "This is very, very strange. The lack of communication is puzzling. How the pilots are not communicating." 
 
 Huzlan has come up with his own theories. 
 
 "From (the) second or third day, I've come to my own private conclusion that it must have been unlawful human interference," he said. "It could have been anyone on the airplane." 
 
 CNN has talked to more than half a dozen U.S. military and intelligence officials who emphasize that while no one knows what happened to the plane, it is more logical to conclude it crashed into the Indian Ocean. 
 
 The officials say there is no evidence that any U.S. satellite data registered an unknown aircraft in any of the Asian countries along the path the plane may have taken. According to these officials, it is overwhelmingly likely if the plane had crashed on land, there would be some evidence of that, and if it had landed, someone would have seen it. 
 
 U.S. Defense Secretary Chuck Hagel raised the issue of transparency when he spoke with his Malaysian counterpart Monday, according to two U.S. officials. 
 
 Both officials said it was not a criticism of the Malaysians, but more a discussion about the need to share information with the world on one of the most complex search operations in history. 
 
 "He was saying the best way to handle this is to continue to be transparent and tell what you know when you know it," one official said of Hagel's conversation. In the first days after the incident, some U.S. officials had said the Malaysian government did not share enough radar and technical data about the flight. 
 
 Malaysian officials have defended their handling of the crisis, stressing that the situation is unprecedented. 
 
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 Key moments emerge in tracking plane ||||| Story highlights Japan to join 8 other nations in search, ministry says 
 
 Plane's transponder had stopped, Malaysian Air Force official says 
 
 Missing flight was way off course, heading in wrong direction, official says 
 
 Experts unsure on what caused transponder to go off, what it means for plane 
 
 It was 1:30 a.m. when Malaysia Airlines Flight 370 lost all communications, including important transponder signals that send data on altitude, direction and speed. Still, it showed up on radar for about 1 hour, 10 minutes longer -- until it vanished, having apparently moved away from its intended destination, hundreds of miles off course. 
 
 Those details -- told to CNN by a senior Malaysian air force official, who declined to be named because he is not authorized to speak to the media -- seemingly shed more light on what happened to the aircraft that mysteriously went missing early Saturday. 
 
 But if these assertions are true -- and other reports, citing a different Malaysian official, cast doubt on them -- many big questions remain. Why were the communications lost? Why was the Boeing 777 going the direction it was? And where did it end up? 
 
 "Something happened to that airplane, that was obviously out of the norm, that caused it to depart from its normal flight path," said Mark Weiss, a former 777 pilot now with the Washington-based Spectrum Group consulting firm. "... It's difficult not to speculate." 
 
 Peter Goelz, former managing director of the National Transportation Safety Board, thinks all this information -- if correct -- ominously suggests that someone purposefully cut off the transponder and steered the plane from its intended destination. 
 
 "This kind of deviation in course is simply inexplicable," said Goelz. 
 
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 Other experts aren't convinced that there were bad actors -- be they hijackers or an ill-intentioned crew member. They say there could have been some sort of sudden catastrophic electronic failure or more that spurred the crew to try to turn around, with no luck. 
 
 "Perhaps there was a power problem," said veteran pilot Kit Darby, former president of Aviation Information Resources, adding that backup power systems would only last about an hour. "(It is) natural for the pilot, in my view, to return to where he knows the airports." 
 
 Still, while they have theories, even those who have piloted massive commercial airliners like this one admit that they can't conclude anything until the plane is found. For now, the massive multinational search has yielded no breakthrough -- which has only added to the heartache for the friends and family of the 239 passengers and crew on board. 
 
 The Malaysian air force official's revelations may provide more direction, though clarity and closure are still elusive. 
 
 "There are still as many possibilities out there, maybe more, now that we know about the transponders being off and the length of time that plane flew in the air without them," said CNN law enforcement analyst Tom Fuentes. "It still leaves mechanical, terrorism (and) other issues as much in the air as they were before." 
 
 Intentional or catastrophic mechanical failure? 
 
 According to the Malaysian air force official, the plane's transponder apparently stopped working at about the time flight controllers lost contact with it, near the coast of Vietnam. 
 
 The air force eventually and totally lost track of the plane over Pulau Perak, a tiny island in the Strait of Malacca -- many hundreds of miles from the usual flight path for aircraft traveling between Kuala Lumpur and Beijing, the official said. 
 
 If the data cited by the source is correct, the aircraft was flying away from Beijing and on the opposite side of the Malay Peninsula from its scheduled route. 
 
 Why would the transponder -- an electrical instrument in commercial airline cockpits that continuously transmits information such as altitude, location, direction and speed -- have gone off? 
 
 Goelz, the former NTSB managing director, and others point out the only reason for someone to intentionally turn off the transponder is to conceal the plane's location and direction. Someone with nefarious intentions of taking over an aircraft and steering it to where it wasn't supposed to be -- or perhaps planning on crashing it -- might do just that. 
 
 "You have to have a very deliberate process to turn the transponder off," he said. "... There might still be mechanical explanations on what was going on, but those mechanical explanations are narrowing quickly." 
 
 Anthony Roman, a trained pilot and consultant, said that a fast-moving fire might have moved through the cockpit and rendered everything, including the crew, effectively powerless to do much more than turn the plane around. 
 
 "Fires are insidious," Roman told CNN's Wolf Blitzer. "They can happen quickly and knock out multiple systems quickly." 
 
 Darby, for one, believes purely mechanical issues remain the most valid possibility now. His main point is: "Everything is electrical." In other words, if there's some sort of "catastrophic failure" for whatever reason, that could knock out systems like the transponder. 
 
 If that would happen, the plane could fly for some time without electricity but not indefinitely. Any attempts to steer it would be harder in the dark without functioning flight instruments said Darby, a retired United captain. 
 
 Whether the air force official's account is true, that possibility and others make the mystery more and more confounding. 
 
 Photos: The search for MH370 Photos: The search for MH370 In late February 2016, American tourist Blaine Gibson found a piece of plane debris off Mozambique, a discovery that renewed hope of solving the mystery of missing Malaysia Airlines Flight 370. The piece measures 35 inches by 22 inches. A U.S. official said it was likely the wreckage came from a Boeing 777, like MH370. Others were more skeptical. Hide Caption 1 of 41 Photos: The search for MH370 On July 29, police carry a piece of debris on Reunion Island , a French territory in the Indian Ocean. A week later, authorities confirmed that the debris was from MH370, which disappeared on March 8, 2014. Hide Caption 2 of 41 Photos: The search for MH370 Relatives of the flight's passengers console each other outside the Malaysia Airlines office in Subang, Malaysia, on February 12, 2015. Protesters had demanded that the airline withdraw the statement that all 239 people aboard the plane were dead. Hide Caption 3 of 41 Photos: The search for MH370 A police officer watches a couple cry outside the airline's office building in Beijing after officials refused to meet with them on June 11, 2014. The couple's son was on the plane. Hide Caption 4 of 41 Photos: The search for MH370 Members of the media scramble to speak with Azharuddin Abdul Rahman, director general of Malaysia's Civil Aviation Department, at a hotel in Kuala Lumpur, Malaysia, on May 27, 2014. Data from communications between satellites and the missing flight was released the day before, more than two months after relatives of passengers said they requested it be made public. Hide Caption 5 of 41 Photos: The search for MH370 Operators aboard the Australian ship Ocean Shield move Bluefin-21, the U.S. Navy's autonomous underwater vehicle, into position to search for the jet on April 14, 2014. Hide Caption 6 of 41 Photos: The search for MH370 A member of the Royal New Zealand Air Force looks out of a window while searching for debris off the coast of western Australia on April 13, 2014. Hide Caption 7 of 41 Photos: The search for MH370 The HMS Echo, a vessel with the British Roya; Navy, moves through the waters of the southern Indian Ocean on April 12, 2014. Hide Caption 8 of 41 Photos: The search for MH370 A Royal Australian Air Force AP-3C Orion, on a mission to drop sonar buoys to assist in the search, flies past the Australian vessel Ocean Shield on April 9, 2014. Hide Caption 9 of 41 Photos: The search for MH370 A relative of a missing passenger cries at a vigil in Beijing on April 8, 2014. Hide Caption 10 of 41 Photos: The search for MH370 Australian Defense Force divers scan the water for debris in the southern Indian Ocean on April 7, 2014. Hide Caption 11 of 41 Photos: The search for MH370 A towed pinger locator is readied to be deployed off the deck of the Australian vessel Ocean Shield on April 7, 2014. Hide Caption 12 of 41 Photos: The search for MH370 A member of the Royal New Zealand Air Force looks at a flare in the Indian Ocean during search operations on April 4, 2014. Hide Caption 13 of 41 Photos: The search for MH370 On March 30, 2014, a woman in Kuala Lumpur prepares for an event in honor of those aboard Flight 370. Hide Caption 14 of 41 Photos: The search for MH370 The sole representative for the families of Flight 370 passengers leaves a conference at a Beijing hotel on March 28, 2014, after other relatives left en masse to protest the Malaysian government's response to their questions. Hide Caption 15 of 41 Photos: The search for MH370 A member of the Royal Australian Air Force is silhouetted against the southern Indian Ocean during the search for the missing jet on March 27, 2014. Hide Caption 16 of 41 Photos: The search for MH370 Flight Lt. Jayson Nichols looks at a map aboard a Royal Australian Air Force aircraft during a search on March 27, 2014. Hide Caption 17 of 41 Photos: The search for MH370 People in Kuala Lumpur light candles during a ceremony held for the missing flight's passengers on March 27, 2014. Hide Caption 18 of 41 Photos: The search for MH370 Malaysian Prime Minister Najib Razak, center, delivers a statement about the flight on March 24, 2014. Razak's announcement came after the airline sent a text message to relatives saying it "deeply regrets that we have to assume beyond any reasonable doubt that MH 370 has been lost and that none of those onboard survived." Hide Caption 19 of 41 Photos: The search for MH370 Grieving relatives of missing passengers leave a hotel in Beijing on March 24, 2014. Hide Caption 20 of 41 Photos: The search for MH370 A passenger views a weather map in the departures terminal of Kuala Lumpur International Airport on March 22, 2014. Hide Caption 21 of 41 Photos: The search for MH370 A Chinese satellite captured this image, released on March 22, 2014, of a floating object in the Indian Ocean, according to China's State Administration of Science. It was a possible lead in the search for the missing plane. Surveillance planes were looking for two objects spotted by satellite imagery in remote, treacherous waters more than 1,400 miles from the west coast of Australia. Hide Caption 22 of 41 Photos: The search for MH370 Satellite imagery provided by the Australian Maritime Safety Authority on March 20, 2014, showed debris in the southern Indian Ocean that could have been from Flight 370. The announcement by Australian officials raised hopes of a breakthrough in the frustrating search. Hide Caption 23 of 41 Photos: The search for MH370 Another satellite shot provided by the Australian Maritime Safety Authority shows possible debris from the flight. Hide Caption 24 of 41 Photos: The search for MH370 A distraught relative of a missing passenger breaks down while talking to reporters at Kuala Lumpur International Airport on March 19, 2014. Hide Caption 25 of 41 Photos: The search for MH370 On March 18, 2014, a relative of a missing passenger tells reporters in Beijing about a hunger strike to protest authorities' handling of information about the missing jet. Hide Caption 26 of 41 Photos: The search for MH370 U.S. Navy crew members assist in search-and-rescue operations in the Indian Ocean on March 16, 2014. Hide Caption 27 of 41 Photos: The search for MH370 Members of the Chinese navy continue search operations on March 13, 2014. After starting in the sea between Malaysia and Vietnam, the plane's last confirmed location, search efforts expanded west into the Indian Ocean. Hide Caption 28 of 41 Photos: The search for MH370 A Vietnamese military official looks out an aircraft window during search operations March 13, 2014. Hide Caption 29 of 41 Photos: The search for MH370 Malaysian air force members look for debris near Kuala Lumpur on March 13, 2014. Hide Caption 30 of 41 Photos: The search for MH370 Relatives of missing passengers wait for the latest news at a hotel in Beijing on March 12, 2014. Hide Caption 31 of 41 Photos: The search for MH370 A member of the Vietnamese air force checks a map while searching for the missing plane on March 11, 2014. Hide Caption 32 of 41 Photos: The search for MH370 A Vietnamese air force plane found traces of oil that authorities had suspected to be from the missing Malaysia Airlines plane, the Vietnamese government online newspaper reported on March 8, 2014. However, a sample from the slick showed it was bunker oil, typically used to power large cargo ships, Malaysia's state news agency, Bernama, reported on March 10, 2014. Hide Caption 33 of 41 Photos: The search for MH370 A U.S. Navy Seahawk helicopter lands aboard the USS Pinckney to change crews on March 9, 2014, before returning to search for the missing plane in the Gulf of Thailand. Hide Caption 34 of 41 Photos: The search for MH370 Buddhist monks at Kuala Lumpur International Airport offer a special prayer for the missing passengers on March 9, 2014. Hide Caption 35 of 41 Photos: The search for MH370 Members of a Chinese emergency response team board a rescue vessel at the port of Sanya in China's Hainan province on March 9, 2014. Hide Caption 36 of 41 Photos: The search for MH370 The rescue vessel sets out from Sanya in the South China Sea on March 9, 2014. Hide Caption 37 of 41 Photos: The search for MH370 Malaysian Prime Minister Najib Razak, center, arrives to meet family members of missing passengers at the reception center at Kuala Lumpur International Airport on March 8, 2014. Hide Caption 38 of 41 Photos: The search for MH370 A relative of two missing passengers reacts at their home in Kuala Lumpur on March 8, 2014. Hide Caption 39 of 41 Photos: The search for MH370 Chinese police at the Beijing airport stand beside the arrival board showing delayed Flight 370 in red on March 8, 2014. Hide Caption 40 of 41 Photos: The search for MH370 Malaysia Airlines Group CEO Ahmad Juahari Yahya, front, speaks during a news conference at a hotel in Sepang on March 8, 2014. "We deeply regret that we have lost all contacts" with the jet, he said. Hide Caption 41 of 41 
 
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 "You couldn't make this story up," said Michael Goldfarb, a former official with the Federal Aviation Administration. 
 
 Terrorism a possibility 
 
 Authorities have said they're looking at all possibilities to explain what happened to the Malaysia Airlines aircraft. 
 
 Earlier Tuesday, the head of the international police organization Interpol said that his agency increasingly believed the incident was not related to terrorism. 
 
 "The more information we get, the more we're inclined to conclude that it was not a terrorist incident," Interpol Secretary General Ronald Noble said at a news conference in Lyon, France. 
 
 Yet -- speaking Tuesday about what he called a "very disturbing mystery" -- CIA Director John Brennan insisted terrorism remains a possibility. 
 
 "I don't know (what happened)," he said. "But I don't think people should, at this point, rule out any of these lines of inquiry." 
 
 The two passengers who have dominated headlines the last two days entered Malaysia using valid Iranian passports, Noble said. But they used stolen Austrian and Italian passports to board the missing Malaysian plane, he said. 
 
 Noble gave their names and ages as Pouri Nourmohammadi, 18, and Delavar Seyed Mohammad Reza, 29. 
 
 Malaysian police had earlier identified Nourmohammadi, using a slightly different name and age, and said they believed he was trying to migrate to Germany. 
 
 Inspector General Khalid Abu Bakar of the Royal Malaysian Police said it doesn't appear the younger Iranian posed a threat. 
 
 "We have been checking his background," Khalid said, noting "other police organizations" have been consulted. "And we believe that he is not likely to be a member of any terrorist group," Khalid said. 
 
 After he failed to arrive in Frankfurt, the final destination of his ticket, his mother contacted authorities, Khalid said. According to ticketing records, the ticket to Frankfurt was booked under the stolen Austrian passport. 
 
 Extensive search for plane 
 
 No one knows where these two men and the other 237 people on the plane ended up. Every lead that has raised hopes of tracing the commercial jet has so far petered out. 
 
 Over the past few days, search teams have been scouring tens of thousands of square miles of sea between the northeast coast of Malaysia and southwest Vietnam. They have also been searching off the west coast of the Malay Peninsula, in the Strait of Malacca, and north into the Andaman Sea. 
 
 The search also encompasses the land in between the two areas of sea. 
 
 But it could be days, weeks or even months before the searchers find anything that begins to explain what happened to the plane, which disappeared early Saturday en route to Beijing. 
 
 In the case of Air France Flight 447, which disappeared over the Atlantic in 2009, it took five days just to find the first floating wreckage. 
 
 And it was nearly two years before investigators found the bulk of the French plane's wreckage and the majority of the bodies of the 228 people on board, about 12,000 feet below the surface of the ocean. 
 
 The Gulf of Thailand, the area where the missing Malaysian plane was last detected, is much shallower, with a maximum depth of only 260 feet and an average depth of about 150 feet. 
 
 Still, they have to find it first. The newly disclosed revelation about the plane's direction doesn't help, as it means less certainty and more time for currents to move the wreckage around. 
 
 "Crucial time is passing," David Gallo, with the Woods Hole Oceanographic Institution, told CNN's Wolf Blitzer on Monday. "That search area -- that haystack -- is getting bigger and bigger and bigger." 
 
 Thailand, Singapore, Indonesia, Vietnam, Australia, the United States, China and Malaysia are all taking part in the search, White House spokesman Jay Carney said. Japan has also dispatched a team to the area, with Japanese military and coast guard crews likely to follow, its foreign ministry announced Wednesday. 
 
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 That helps takes all forms, such as many as 10 Chinese satellites monitoring the area to the helicopters ready-to-dispatch off of U.S. warships. 
 
 CNN aviation correspondent Richard Quest described the search as "extremely painstaking work," suggesting a grid would have been drawn over the ocean for teams to comb, bit by bit. 
 
 Quest said that the expanding search area shows how little idea rescue officials have of where the plane might be. But he's still confident they'll find it eventually. 
 
 "It's not hopeless, by any means. They will find it," he said. "They have to. They have to know what happened." 
 
 Until they do, patience is growing thin for friends and family members of those aboard Flight 370. 
 
 As a middle-aged man -- the father of one such passenger -- shouted Tuesday at an airline agent in Beijing: "Time is passing by." ||||| Story highlights Official: Programmed change in direction occurred 12 minutes before sign off 
 
 Analyst: "Sometimes an erratic flight path is heroism, not terrorism" 
 
 Law enforcement official: Plane's turn almost certainly programmed from cockpit 
 
 Officials say nothing on pilots' computers, e-mails indicates deviation was planned 
 
 New information from the Thai government bolsters the belief that missing Malaysia Airlines Flight 370 took a sharp westward turn after communication was lost. 
 
 And it looks like that turn was no accident. 
 
 A law enforcement official told CNN Tuesday that the aircraft's first turn to the west was almost certainly programmed by somebody in the cockpit. 
 
 The official, who has been briefed on the investigation, said the programmed change in direction was entered at least 12 minutes before the plane's co-pilot signed off to air traffic controllers, telling them, "All right, good night." 
 
 Analysts on CNN's "AC360" offered different interpretations of what that could mean -- with some experts cautioning the change in direction could have been part of an alternate flight plan programmed in advance in case of emergency, and others warning it could show something more nefarious was afoot. 
 
 "We don't know when specifically it was entered," said Mary Schiavo, a CNN aviation analyst and former inspector general for the U.S. Department of Transportation. 
 
 New York Times reporter Michael Schmidt said the new timeframe "makes the issue of foul play seem more significant." 
 
 "Because by doing that," he said, "what it basically shows is that this thing was already heading in a different direction when they're saying good night." 
 
 But still, the new details about what happened don't add up to a clear answer. 
 
 "Like everything on this story, we learn a little bit," Schmidt said, "but then we just have more questions." 
 
 Evidence that someone programmed the plane's computer and the Thai data that surfaced Tuesday corroborate a leading theory from Malaysian investigators: The missing plane veered off course in a deliberate act by someone who knew what they were doing. 
 
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 Photos: The search for MH370 Photos: The search for MH370 Two years after Malaysia Airlines Flight 370 went missing, a relative of one of the passengers burns incense in Beijing on March 8, 2016. Flight 370 vanished on March 8, 2014, as it flew from Kuala Lumpur, Malaysia, to Beijing. There were 239 people on board. Hide Caption 1 of 43 Photos: The search for MH370 On July 29, police carry a piece of debris on Reunion Island, a French territory in the Indian Ocean. A week later, authorities confirmed that the debris was from the missing flight. Hide Caption 2 of 43 Photos: The search for MH370 Staff members with the Australian Transport Safety Bureau examine a piece of aircraft debris at their laboratory in Canberra, Australia, on July 20. The flap was found in June by residents on Pemba Island off the coast of Tanzania, and officials had said it was highly likely to have come from Flight 370. Experts at the Australian Transport Safety Bureau, which is heading up the search for the plane, confirmed that the part was indeed from the missing aircraft. Hide Caption 3 of 43 Photos: The search for MH370 In late February, American tourist Blaine Gibson found a piece of plane debris off Mozambique, a discovery that renewed hope of solving the mystery of the missing flight. The piece measured 35 inches by 22 inches. A U.S. official said it was likely the wreckage came from a Boeing 777, which MH370 was. Hide Caption 4 of 43 Photos: The search for MH370 Relatives of the flight's passengers console each other outside the Malaysia Airlines office in Subang, Malaysia, on February 12, 2015. Protesters had demanded that the airline withdraw the statement that all 239 people aboard the plane were dead. Hide Caption 5 of 43 Photos: The search for MH370 A police officer watches a couple cry outside the airline's office building in Beijing after officials refused to meet with them on June 11, 2014. The couple's son was on the plane. Hide Caption 6 of 43 Photos: The search for MH370 Members of the media scramble to speak with Azharuddin Abdul Rahman, director general of Malaysia's Civil Aviation Department, at a hotel in Kuala Lumpur, Malaysia, on May 27, 2014. Data from communications between satellites and the missing flight was released the day before, more than two months after relatives of passengers said they requested it be made public. Hide Caption 7 of 43 Photos: The search for MH370 Operators aboard the Australian ship Ocean Shield move Bluefin-21, the U.S. Navy's autonomous underwater vehicle, into position to search for the jet on April 14, 2014. Hide Caption 8 of 43 Photos: The search for MH370 A member of the Royal New Zealand Air Force looks out of a window while searching for debris off the coast of western Australia on April 13, 2014. Hide Caption 9 of 43 Photos: The search for MH370 The HMS Echo, a vessel with the British Roya; Navy, moves through the waters of the southern Indian Ocean on April 12, 2014. Hide Caption 10 of 43 Photos: The search for MH370 A Royal Australian Air Force AP-3C Orion, on a mission to drop sonar buoys to assist in the search, flies past the Australian vessel Ocean Shield on April 9, 2014. Hide Caption 11 of 43 Photos: The search for MH370 A relative of a missing passenger cries at a vigil in Beijing on April 8, 2014. Hide Caption 12 of 43 Photos: The search for MH370 Australian Defense Force divers scan the water for debris in the southern Indian Ocean on April 7, 2014. Hide Caption 13 of 43 Photos: The search for MH370 A towed pinger locator is readied to be deployed off the deck of the Australian vessel Ocean Shield on April 7, 2014. Hide Caption 14 of 43 Photos: The search for MH370 A member of the Royal New Zealand Air Force looks at a flare in the Indian Ocean during search operations on April 4, 2014. Hide Caption 15 of 43 Photos: The search for MH370 On March 30, 2014, a woman in Kuala Lumpur prepares for an event in honor of those aboard Flight 370. Hide Caption 16 of 43 Photos: The search for MH370 The sole representative for the families of Flight 370 passengers leaves a conference at a Beijing hotel on March 28, 2014, after other relatives left en masse to protest the Malaysian government's response to their questions. Hide Caption 17 of 43 Photos: The search for MH370 A member of the Royal Australian Air Force is silhouetted against the southern Indian Ocean during the search for the missing jet on March 27, 2014. Hide Caption 18 of 43 Photos: The search for MH370 Flight Lt. Jayson Nichols looks at a map aboard a Royal Australian Air Force aircraft during a search on March 27, 2014. Hide Caption 19 of 43 Photos: The search for MH370 People in Kuala Lumpur light candles during a ceremony held for the missing flight's passengers on March 27, 2014. Hide Caption 20 of 43 Photos: The search for MH370 Malaysian Prime Minister Najib Razak, center, delivers a statement about the flight on March 24, 2014. Razak's announcement came after the airline sent a text message to relatives saying it "deeply regrets that we have to assume beyond any reasonable doubt that MH 370 has been lost and that none of those onboard survived." Hide Caption 21 of 43 Photos: The search for MH370 Grieving relatives of missing passengers leave a hotel in Beijing on March 24, 2014. Hide Caption 22 of 43 Photos: The search for MH370 A passenger views a weather map in the departures terminal of Kuala Lumpur International Airport on March 22, 2014. Hide Caption 23 of 43 Photos: The search for MH370 A Chinese satellite captured this image, released on March 22, 2014, of a floating object in the Indian Ocean, according to China's State Administration of Science. It was a possible lead in the search for the missing plane. Surveillance planes were looking for two objects spotted by satellite imagery in remote, treacherous waters more than 1,400 miles from the west coast of Australia. Hide Caption 24 of 43 Photos: The search for MH370 Satellite imagery provided by the Australian Maritime Safety Authority on March 20, 2014, showed debris in the southern Indian Ocean that could have been from Flight 370. The announcement by Australian officials raised hopes of a breakthrough in the frustrating search. Hide Caption 25 of 43 Photos: The search for MH370 Another satellite shot provided by the Australian Maritime Safety Authority shows possible debris from the flight. Hide Caption 26 of 43 Photos: The search for MH370 A distraught relative of a missing passenger breaks down while talking to reporters at Kuala Lumpur International Airport on March 19, 2014. Hide Caption 27 of 43 Photos: The search for MH370 On March 18, 2014, a relative of a missing passenger tells reporters in Beijing about a hunger strike to protest authorities' handling of information about the missing jet. Hide Caption 28 of 43 Photos: The search for MH370 U.S. Navy crew members assist in search-and-rescue operations in the Indian Ocean on March 16, 2014. Hide Caption 29 of 43 Photos: The search for MH370 Members of the Chinese navy continue search operations on March 13, 2014. After starting in the sea between Malaysia and Vietnam, the plane's last confirmed location, search efforts expanded west into the Indian Ocean. Hide Caption 30 of 43 Photos: The search for MH370 A Vietnamese military official looks out an aircraft window during search operations March 13, 2014. Hide Caption 31 of 43 Photos: The search for MH370 Malaysian air force members look for debris near Kuala Lumpur on March 13, 2014. Hide Caption 32 of 43 Photos: The search for MH370 Relatives of missing passengers wait for the latest news at a hotel in Beijing on March 12, 2014. Hide Caption 33 of 43 Photos: The search for MH370 A member of the Vietnamese air force checks a map while searching for the missing plane on March 11, 2014. Hide Caption 34 of 43 Photos: The search for MH370 A Vietnamese air force plane found traces of oil that authorities had suspected to be from the missing Malaysia Airlines plane, the Vietnamese government online newspaper reported on March 8, 2014. However, a sample from the slick showed it was bunker oil, typically used to power large cargo ships, Malaysia's state news agency, Bernama, reported on March 10, 2014. Hide Caption 35 of 43 Photos: The search for MH370 A U.S. Navy Seahawk helicopter lands aboard the USS Pinckney to change crews on March 9, 2014, before returning to search for the missing plane in the Gulf of Thailand. Hide Caption 36 of 43 Photos: The search for MH370 Buddhist monks at Kuala Lumpur International Airport offer a special prayer for the missing passengers on March 9, 2014. Hide Caption 37 of 43 Photos: The search for MH370 Members of a Chinese emergency response team board a rescue vessel at the port of Sanya in China's Hainan province on March 9, 2014. Hide Caption 38 of 43 Photos: The search for MH370 The rescue vessel sets out from Sanya in the South China Sea on March 9, 2014. Hide Caption 39 of 43 Photos: The search for MH370 Malaysian Prime Minister Najib Razak, center, arrives to meet family members of missing passengers at the reception center at Kuala Lumpur International Airport on March 8, 2014. Hide Caption 40 of 43 Photos: The search for MH370 A relative of two missing passengers reacts at their home in Kuala Lumpur on March 8, 2014. Hide Caption 41 of 43 Photos: The search for MH370 Chinese police at the Beijing airport stand beside the arrival board showing delayed Flight 370 in red on March 8, 2014. Hide Caption 42 of 43 Photos: The search for MH370 Malaysia Airlines Group CEO Ahmad Juahari Yahya, front, speaks during a news conference at a hotel in Sepang on March 8, 2014. "We deeply regret that we have lost all contacts" with the jet, he said. Hide Caption 43 of 43 
 
 But investigators still don't know who was at the controls, or why whoever was flying the plane apparently took it far from its original destination. 
 
 An initial search of the pilots' personal computers and e-mails found nothing to indicate that the sudden deviation in the aircraft's route was planned, U.S. officials said Tuesday after being briefed by Malaysian authorities. 
 
 The officials said they had also reviewed cockpit conversations between the plane and air traffic controllers and heard nothing suspicious or anything that would explain why the jetliner changed course. 
 
 And a flight simulator belonging to pilot Zaharie Ahmad Shah did not show any of the unexplained paths the plane may have flown after it went off the grid, officials said. 
 
 Schiavo said it's no surprise investigators found nothing suspicious in the pilots' homes. 
 
 "I've worked on many cases were the pilots were suspect, and it turned out to be a mechanical and horrible problem," she said. "And I have a saying myself: Sometimes an erratic flight path is heroism, not terrorism. And I always remind myself of that, not to jump to that conclusion. Sometimes pilots are fighting amazing battles, and we never hear about it. " 
 
 Thailand: Plane sent intermittent signal 
 
 The Thai military's revelation that it also spotted the plane turning west toward the Strait of Malacca is one encouraging sign that investigators could be on the right track after days of searching for the missing plane have failed to turn up any answers about its location. 
 
 The Thai military was receiving normal flight path and communication data from the Boeing 777-200 on its planned March 8 route from Kuala Lumpur to Beijing until 1:22 a.m., when it disappeared from its radar. 
 
 Six minutes later, the Thai military detected an unknown signal, a Royal Thai Air Force spokesman told CNN. This unknown aircraft, possibly Flight 370, was heading the opposite direction. 
 
 Malaysia says the evidence suggests that the plane was deliberately flown off-course, turning west and traveling back over the Malay Peninsula and out into the Indian Ocean. 
 
 The Thai data are the second radar evidence that the plane did indeed turn around toward the Strait of Malacca. 
 
 It follows information from the Malaysian air force that its military radar tracked the plane as it passed over the small island of Pulau Perak in the Strait of Malacca. 
 
 "The unknown aircraft's signal was sending out intermittently, on and off and on and off," the spokesman said. The Thai military lost the unknown aircraft's signal because of the limits of its military radar, he said. 
 
 Investigators say they're still not sure where the plane ended up. 
 
 The latest findings say the plane's last known location detected by a satellite is along two wide arcs: one stretching north over Asia and the other south into the Indian Ocean. The plane's last electronic connection with the satellite was about six hours after it last showed up on Malaysian military radar. 
 
 The total area now being searched stands at 2.97 million square miles -- an area nearly the size of the continental United States -- Hishammuddin Hussein, the Malaysian defense and transport minister said. 
 
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 "This is an enormous search area," Hishammuddin said. "And it is something that Malaysia cannot possibly search on its own. I am therefore very pleased that so many countries have come forward to offer assistance and support to the search and rescue operation." 
 
 Turn made by computer? 
 
 The pilot and first officer of the missing plane, both of them Malaysian, have come under particular scrutiny in the search for clues. 
 
 But officials have reported no evidence to tie the pilot and first officer to the plane's disappearance. 
 
 One aviation expert, writing an opinion piece for CNN.com , floated the idea last week that whoever changed the plane's course was an expert. 
 
 The cockpit computer programming analysis, first reported by The New York Times Tuesday, has increased investigators' focus on the pilot and first officer, the newspaper said. 
 
 Asked about the report Tuesday, Malaysia Airlines Chief Executive Ahmad Jauhari Yahya said, "As far as we're concerned, the aircraft was programmed to fly to Beijing. That's the standard procedure." 
 
 But he didn't rule out the possibility the flight path had been reprogrammed. 
 
 "Once you're in the aircraft," he said, "anything is possible." 
 
 China clears citizens 
 
 China says it has found no evidence that any of its citizens on board the missing plane were involved in hijacking or terrorism. 
 
 Background checks on all passengers from the Chinese mainland on the plane have found nothing to support such suspicions, Huang Huikang, the Chinese ambassador to Malaysia, said Tuesday, according to the state-run Chinese news agency Xinhua. 
 
 Authorities have said they are investigating all 239 people who were on board the flight, which disappeared more than 10 days ago. 
 
 According to the airline, 153 of the 227 passengers on board the plane came from mainland China or Hong Kong. 
 
 By effectively ruling out suspicions for a large majority of the passengers, Chinese authorities appear to have significantly shortened the list of possible suspects in the investigation. 
 
 The Chinese ambassador's statement is also likely to greatly dampen speculation that Uyghur separatists from China's far western region of Xinjiang might have been involved in the plane's disappearance. 
 
 One of the two long corridors where authorities say the plane was last detected stretched over Xinjiang, and unconfirmed reports had suggested the possibility that Uyghurs might be connected to the case. 
 
 Chinese authorities have accused separatists from Xinjiang of carrying out a terrorist attack this month in which eight attackers armed with long knives stormed a train station in Kunming, a city in southwestern China, killing 29 people and wounding more than 140. 
 
 China said Tuesday that it had begun to search for the plane in the parts of its territory that fall under the northern corridor, deploying satellite and radar resources. 
 
 Experts are analyzing past and present data along the arc stretching through Chinese territory, Hong Lei, a Foreign Ministry spokesman, said at a news briefing Tuesday in Beijing. 
 
 Still a mystery 
 
 Eleven days after Flight 370 disappeared, the bottom line is that the fate of the flight remains a mystery. As time has passed, initial theories about mechanical error have led to more elaborate ideas about complicated hijacking or commandeering plots. 
 
 Former Malaysia Airlines pilot Nik Huzlan has flown the same aircraft that is now missing. 
 
 "I know, I flew this plane," he said. "This is very, very strange. The lack of communication is puzzling. How the pilots are not communicating." 
 
 Huzlan has come up with his own theories. 
 
 "From (the) second or third day, I've come to my own private conclusion that it must have been unlawful human interference," he said. "It could have been anyone on the airplane." 
 
 CNN has talked to more than half a dozen U.S. military and intelligence officials who emphasize that while no one knows what happened to the plane, it is more logical to conclude it crashed into the Indian Ocean. 
 
 The officials say there is no evidence that any U.S. satellite data registered an unknown aircraft in any of the Asian countries along the path the plane may have taken. According to these officials, it is overwhelmingly likely if the plane had crashed on land, there would be some evidence of that, and if it had landed, someone would have seen it. 
 
 U.S. Defense Secretary Chuck Hagel raised the issue of transparency when he spoke with his Malaysian counterpart Monday, according to two U.S. officials. 
 
 Both officials said it was not a criticism of the Malaysians, but more a discussion about the need to share information with the world on one of the most complex search operations in history. 
 
 "He was saying the best way to handle this is to continue to be transparent and tell what you know when you know it," one official said of Hagel's conversation. In the first days after the incident, some U.S. officials had said the Malaysian government did not share enough radar and technical data about the flight. ||||| Story highlights CNN analysts say figuring out motive of whoever steered plane off course is key 
 
 Background checks on some passengers complete with no red flags 
 
 Chinese families lose patience with Malaysian government and Malaysia Airlines 
 
 Authorities still looking at flight simulator taken from pilot's home 
 
 Where do you even begin to look, when the search area covers vast swaths of land and water, stretching thousands of miles, from Kazakhstan to the Indian Ocean? 
 
 That's the question for Malaysian officials and authorities from 24 other nations as people search for a ninth day, trying to find Malaysia Airlines Flight 370 and the 239 people on board. 
 
 As the search area grows bigger, authorities are also increasing their scrutiny of the pilots, searching their homes in the quest for clues. That includes a flight simulator from the captain's home. 
 
 It also includes interviewing the engineers who were in contact with MH370 before it took off, according to a statement from acting Transport Minister Datuk Seri Hishammuddin Tun Hussein to BERNAMA, Malaysia's official news agency. The transport minister characterized the interviews as "normal procedure." 
 
 "Police are still working on it. ... Nothing conclusive yet," a senior police official who has direct knowledge of the investigation told CNN on Sunday night, speaking on the condition of anonymity because the official was not authorized to speak to the press. 
 
 Photos: The search for MH370 Photos: The search for MH370 Two years after Malaysia Airlines Flight 370 went missing, a relative of one of the passengers burns incense in Beijing on March 8, 2016. Flight 370 vanished on March 8, 2014, as it flew from Kuala Lumpur, Malaysia, to Beijing. There were 239 people on board. Hide Caption 1 of 43 Photos: The search for MH370 On July 29, police carry a piece of debris on Reunion Island, a French territory in the Indian Ocean. A week later, authorities confirmed that the debris was from the missing flight. Hide Caption 2 of 43 Photos: The search for MH370 Staff members with the Australian Transport Safety Bureau examine a piece of aircraft debris at their laboratory in Canberra, Australia, on July 20. The flap was found in June by residents on Pemba Island off the coast of Tanzania, and officials had said it was highly likely to have come from Flight 370. Experts at the Australian Transport Safety Bureau, which is heading up the search for the plane, confirmed that the part was indeed from the missing aircraft. Hide Caption 3 of 43 Photos: The search for MH370 In late February, American tourist Blaine Gibson found a piece of plane debris off Mozambique, a discovery that renewed hope of solving the mystery of the missing flight. The piece measured 35 inches by 22 inches. A U.S. official said it was likely the wreckage came from a Boeing 777, which MH370 was. Hide Caption 4 of 43 Photos: The search for MH370 Relatives of the flight's passengers console each other outside the Malaysia Airlines office in Subang, Malaysia, on February 12, 2015. Protesters had demanded that the airline withdraw the statement that all 239 people aboard the plane were dead. Hide Caption 5 of 43 Photos: The search for MH370 A police officer watches a couple cry outside the airline's office building in Beijing after officials refused to meet with them on June 11, 2014. The couple's son was on the plane. Hide Caption 6 of 43 Photos: The search for MH370 Members of the media scramble to speak with Azharuddin Abdul Rahman, director general of Malaysia's Civil Aviation Department, at a hotel in Kuala Lumpur, Malaysia, on May 27, 2014. Data from communications between satellites and the missing flight was released the day before, more than two months after relatives of passengers said they requested it be made public. Hide Caption 7 of 43 Photos: The search for MH370 Operators aboard the Australian ship Ocean Shield move Bluefin-21, the U.S. Navy's autonomous underwater vehicle, into position to search for the jet on April 14, 2014. Hide Caption 8 of 43 Photos: The search for MH370 A member of the Royal New Zealand Air Force looks out of a window while searching for debris off the coast of western Australia on April 13, 2014. Hide Caption 9 of 43 Photos: The search for MH370 The HMS Echo, a vessel with the British Roya; Navy, moves through the waters of the southern Indian Ocean on April 12, 2014. Hide Caption 10 of 43 Photos: The search for MH370 A Royal Australian Air Force AP-3C Orion, on a mission to drop sonar buoys to assist in the search, flies past the Australian vessel Ocean Shield on April 9, 2014. Hide Caption 11 of 43 Photos: The search for MH370 A relative of a missing passenger cries at a vigil in Beijing on April 8, 2014. Hide Caption 12 of 43 Photos: The search for MH370 Australian Defense Force divers scan the water for debris in the southern Indian Ocean on April 7, 2014. Hide Caption 13 of 43 Photos: The search for MH370 A towed pinger locator is readied to be deployed off the deck of the Australian vessel Ocean Shield on April 7, 2014. Hide Caption 14 of 43 Photos: The search for MH370 A member of the Royal New Zealand Air Force looks at a flare in the Indian Ocean during search operations on April 4, 2014. Hide Caption 15 of 43 Photos: The search for MH370 On March 30, 2014, a woman in Kuala Lumpur prepares for an event in honor of those aboard Flight 370. Hide Caption 16 of 43 Photos: The search for MH370 The sole representative for the families of Flight 370 passengers leaves a conference at a Beijing hotel on March 28, 2014, after other relatives left en masse to protest the Malaysian government's response to their questions. Hide Caption 17 of 43 Photos: The search for MH370 A member of the Royal Australian Air Force is silhouetted against the southern Indian Ocean during the search for the missing jet on March 27, 2014. Hide Caption 18 of 43 Photos: The search for MH370 Flight Lt. Jayson Nichols looks at a map aboard a Royal Australian Air Force aircraft during a search on March 27, 2014. Hide Caption 19 of 43 Photos: The search for MH370 People in Kuala Lumpur light candles during a ceremony held for the missing flight's passengers on March 27, 2014. Hide Caption 20 of 43 Photos: The search for MH370 Malaysian Prime Minister Najib Razak, center, delivers a statement about the flight on March 24, 2014. Razak's announcement came after the airline sent a text message to relatives saying it "deeply regrets that we have to assume beyond any reasonable doubt that MH 370 has been lost and that none of those onboard survived." Hide Caption 21 of 43 Photos: The search for MH370 Grieving relatives of missing passengers leave a hotel in Beijing on March 24, 2014. Hide Caption 22 of 43 Photos: The search for MH370 A passenger views a weather map in the departures terminal of Kuala Lumpur International Airport on March 22, 2014. Hide Caption 23 of 43 Photos: The search for MH370 A Chinese satellite captured this image, released on March 22, 2014, of a floating object in the Indian Ocean, according to China's State Administration of Science. It was a possible lead in the search for the missing plane. Surveillance planes were looking for two objects spotted by satellite imagery in remote, treacherous waters more than 1,400 miles from the west coast of Australia. Hide Caption 24 of 43 Photos: The search for MH370 Satellite imagery provided by the Australian Maritime Safety Authority on March 20, 2014, showed debris in the southern Indian Ocean that could have been from Flight 370. The announcement by Australian officials raised hopes of a breakthrough in the frustrating search. Hide Caption 25 of 43 Photos: The search for MH370 Another satellite shot provided by the Australian Maritime Safety Authority shows possible debris from the flight. Hide Caption 26 of 43 Photos: The search for MH370 A distraught relative of a missing passenger breaks down while talking to reporters at Kuala Lumpur International Airport on March 19, 2014. Hide Caption 27 of 43 Photos: The search for MH370 On March 18, 2014, a relative of a missing passenger tells reporters in Beijing about a hunger strike to protest authorities' handling of information about the missing jet. Hide Caption 28 of 43 Photos: The search for MH370 U.S. Navy crew members assist in search-and-rescue operations in the Indian Ocean on March 16, 2014. Hide Caption 29 of 43 Photos: The search for MH370 Members of the Chinese navy continue search operations on March 13, 2014. After starting in the sea between Malaysia and Vietnam, the plane's last confirmed location, search efforts expanded west into the Indian Ocean. Hide Caption 30 of 43 Photos: The search for MH370 A Vietnamese military official looks out an aircraft window during search operations March 13, 2014. Hide Caption 31 of 43 Photos: The search for MH370 Malaysian air force members look for debris near Kuala Lumpur on March 13, 2014. Hide Caption 32 of 43 Photos: The search for MH370 Relatives of missing passengers wait for the latest news at a hotel in Beijing on March 12, 2014. Hide Caption 33 of 43 Photos: The search for MH370 A member of the Vietnamese air force checks a map while searching for the missing plane on March 11, 2014. Hide Caption 34 of 43 Photos: The search for MH370 A Vietnamese air force plane found traces of oil that authorities had suspected to be from the missing Malaysia Airlines plane, the Vietnamese government online newspaper reported on March 8, 2014. However, a sample from the slick showed it was bunker oil, typically used to power large cargo ships, Malaysia's state news agency, Bernama, reported on March 10, 2014. Hide Caption 35 of 43 Photos: The search for MH370 A U.S. Navy Seahawk helicopter lands aboard the USS Pinckney to change crews on March 9, 2014, before returning to search for the missing plane in the Gulf of Thailand. Hide Caption 36 of 43 Photos: The search for MH370 Buddhist monks at Kuala Lumpur International Airport offer a special prayer for the missing passengers on March 9, 2014. Hide Caption 37 of 43 Photos: The search for MH370 Members of a Chinese emergency response team board a rescue vessel at the port of Sanya in China's Hainan province on March 9, 2014. Hide Caption 38 of 43 Photos: The search for MH370 The rescue vessel sets out from Sanya in the South China Sea on March 9, 2014. Hide Caption 39 of 43 Photos: The search for MH370 Malaysian Prime Minister Najib Razak, center, arrives to meet family members of missing passengers at the reception center at Kuala Lumpur International Airport on March 8, 2014. Hide Caption 40 of 43 Photos: The search for MH370 A relative of two missing passengers reacts at their home in Kuala Lumpur on March 8, 2014. Hide Caption 41 of 43 Photos: The search for MH370 Chinese police at the Beijing airport stand beside the arrival board showing delayed Flight 370 in red on March 8, 2014. Hide Caption 42 of 43 Photos: The search for MH370 Malaysia Airlines Group CEO Ahmad Juahari Yahya, front, speaks during a news conference at a hotel in Sepang on March 8, 2014. "We deeply regret that we have lost all contacts" with the jet, he said. Hide Caption 43 of 43 
 
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 With news that the Boeing 777-200ER might have flown for six and a half hours after its transponder stopped sending signals March 8, officials said the expanding search area extends over 11 countries, stretching as far north as Kazakhstan, a large nation in Central Asia far from any ocean. 
 
 "This is a significant recalibration of the search," Malaysia's acting Transportation Minister Hishammuddin Hussein said Sunday. 
 
 There are still more questions than answers about the missing flight. Figuring out the motive of whoever apparently steered the plane off course is key, analysts told CNN Sunday. 
 
 "I think they had an end game in mind from the very beginning," CNN aviation analyst Jim Tilmon said, "and they have executed a lot of things that have led us down a road. Are we going to the right place? I'm not sure." 
 
 The plane disappeared on March 8, en route from Kuala Lumpur to Beijing. Airline CEO Ahmad Jauhari Yahya said Sunday the missing passenger jet took off with its normal amount of fuel needed for the roughly six-hour flight and did not have extra fuel on board that could have extended its range. 
 
 One of the nations involved in the search, Pakistan, said Sunday that the plane never showed up on its civilian radars and would have been treated as a threat if it had. 
 
 The Times of India reported that India's military also said there was no way the plane could have flown over India without being picked up on radar. 
 
 A study of the flight's cargo manifest showed there were no dangerous materials on board that concerned investigators, he told reporters. 
 
 Investigators are still looking into the backgrounds of the passengers to see whether any of them were trained pilots. 
 
 "There are still a few countries who have yet to respond to our request for a background check," said Khalid Abu Bakar, inspector general of the Royal Malaysian Police Force. "But there are a few ... foreign intelligence agencies who have cleared all the(ir) passengers." 
 
 U.S. intelligence officials are leaning toward the theory that "those in the cockpit" -- the captain and co-pilot -- were responsible for the mysterious disappearance, a U.S. official with direct knowledge of the latest thinking told CNN. 
 
 The official emphasized no final conclusions have been drawn and all the internal intelligence discussions are based on preliminary assessments of what is known to date. 
 
 Malaysian Prime Minister Najib Razak told reporters on Saturday that the plane veered off course due to apparent deliberate action taken by somebody on board. 
 
 'Someone acting deliberately' 
 
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 The first clue that the captain or co-pilot may have been involved stems from when the plane made a sharp, deliberate turn just after it last communicated with Kuala Lumpur air traffic controllers, and before it would have to communicate with Vietnamese controllers, according to the U.S. official with knowledge of the latest intelligence thinking. 
 
 "This is the perfect place to start to disappear," the official said. 
 
 Adding to the intrigue, ABC News reported that the dramatic left turn was preprogrammed into the plane's navigation computer. It's a task that would have required extensive piloting experience. 
 
 Two senior law enforcement officials also told ABC that new information revealed the plane performed "tactical evasion maneuvers" after it disappeared from radar. CNN was unable to confirm these reports. 
 
 Military radar showed the jetliner flew in a westerly direction back over the Malaysian Peninsula, Najib said. It is then believed to have either turned northwest toward the Bay of Bengal or southwest elsewhere in the Indian Ocean, he said. 
 
 "Evidence is consistent with someone acting deliberately from inside the plane," the Prime Minister said, officially confirming the plane's disappearance was not caused by an accident. "Despite media reports that the plane was hijacked, we are investigating all major possibilities on what caused MH370 to deviate." 
 
 The unconfirmed possibility that the plane could be on land means authorities need to answer that question -- and fast, analysts said. 
 
 "Time is even more of the essence. If this airplane has been taken to be used as a weapon, then the time that has been taken to prepare the aircraft for whatever deed is the plan, obviously to thwart that, it's all about time," said Shawn Pruchnicki, who teaches aviation safety and accident investigation at The Ohio State University. 
 
 Tilmon said whoever deliberately steered the plane off course likely did it with help. But what's next is anyone's guess, he said. 
 
 "We have been behind them all along, so now, if they had a plan, and if that plan included being able to set down someplace and refuel a little bit, we are looking at something that we may never see the end of," he said. 
 
 The pilots 
 
 On Saturday, Malaysian police searched the home of pilot Zaharie Ahmad Shah, 53. Zaharie lives in an upscale, gated community in Shah Alam, outside Malaysia's capital, Kuala Lumpur. 
 
 The Ministry of Transport said Sunday that police were examining a flight simulator found at the pilot's house. 
 
 It's somewhat common among aviation enthusiasts to use online flight simulator programs to replicate various situations. Simulators allow users to virtually experience scenarios in various aircraft. Programs can simulate flight routes, landings and takeoffs from actual airports. 
 
 Two vans were loaded with small bags, similar to shopping bags, at the home of the co-pilot, 27-year-old Fariq Ab Hamid, according to a CNN crew who observed activities at the residence. It was unclear whether the bags were taken from the home, and police made no comment about their activities there. 
 
 Andaman and Nicobar Islands 
 
 Najib made clear in a news conference that in light of the latest developments, authorities have refocused their investigation to the crew, ground staff and passengers on board. 
 
 Hishammuddin, the transportation minister, told reporters the pilots didn't request to work together. 
 
 Peter Chong, a friend of Zaharie's, said he had been in the pilot's house and tried the simulator. 
 
 "It's a reflection of his love for people -- because he wants to share the joy of flying with his friends," Chong said. 
 
 He was bothered by speculation about the captain's credibility and questions about possible ties to terrorism. 
 
 "I think it is a little bit insensitive and unfair to the family," he said, adding he thought there was no evidence to suggest any ulterior motives on Shah's part. 
 
 A senior U.S. law enforcement official told CNN that investigators are carefully reviewing the information so far collected on the pilots to determine whether there is something to indicate a plan or a motive. 
 
 "In any criminal investigation, the most important analysis is what's the motive," said Mary Schiavo, a CNN aviation analyst and former inspector general for the U.S. Department of Transportation. "I think right now, they have to look for it, and they have to rule it out, if they can, with their own pilots, so they can start looking for motives elsewhere." 
 
 Undoubtedly, authorities will scour through the flight manifest and look further to see whether any of the passengers on board had flight training or connections to terror groups. 
 
 According to The New York Times, one of the passengers was an aviation engineer on his way to Beijing to work for a private-jet company. 
 
 Kazakhstan to Indian Ocean 
 
 As the focus of the investigation has shifted, so, too, has the focus of the search. 
 
 Information from international and Malaysian officials indicates the jet may have flown for more than seven hours after the last contact with the pilots. 
 
 Flight 370 took off from Kuala Lumpur at 12:41 a.m. March 8. The last satellite communication from the plane occurred at 8:11 a.m., Najib said, well past the scheduled arrival time in Beijing. It is possible this contact could have been made from the ground, as long as the airplane still had electrical power, Malaysia's civil aviation chief Azharuddin Abdul Rahman said Sunday. 
 
 That last communication, Najib said, was in one of two possible traffic corridors shown on a map released to reporters. A northern arc stretches from the border of Kazakhstan and Turkmenistan to northern Thailand, and a southern arc spans from Indonesia to the southern Indian Ocean. 
 
 "Due to the type of satellite data, we are unable to confirm the precise location of the plane when it last made contact with the satellite," Najib said. 
 
 Because the northern parts of the traffic corridor include some tightly guarded airspace over India, Pakistan and even some U.S. installations in Afghanistan, U.S. authorities believe it more likely the aircraft crashed into waters outside of the reach of radar south of India, a U.S. official told CNN. If it had flown farther north, it's likely it would have been detected by radar. 
 
 Malaysia's Ministry of Transport said Sunday that both the northern and southern corridors are being treated with equal importance. Malaysian officials are working with 25 countries, many of them along the corridors. They include Kazakhstan, Uzbekistan, Kyrgyzstan, Turkmenistan, Pakistan, Bangladesh, India, China, Myanmar, Laos, Vietnam, Thailand, Indonesia, Australia, France, the United Kingdom and the United States. 
 
 Afghanistan's Ministry of Transport said it has joined the search, but said there is no evidence the plane flew over Afghan soil. 
 
 Separately, India has "temporarily halted" its search for the missing plane while Malaysian authorities reassess the situation, according to a top military official. 
 
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 "We are conserving our assets for now," Rear Adm. Sudhir Pillai, the chief of staff of India's joint Andaman and Nicobar command, said Sunday. "We are on a standby." 
 
 He said the Malaysians are reviewing India's deployment. 
 
 Families at boiling point 
 
 For the families and loved ones of those aboard Flight 370, tensions boiled over Sunday in Beijing at the daily briefing by Malaysia Airlines. 
 
 Nine days after the plane went missing, patience is running thin with officials. 
 
 Before a packed room, one man told them that the families have already lost faith. 
 
 "A liar can lie once, twice or three times, but what's the point (to) keep lying?" he said. "What we ask for is the truth. Don't hide things from us." 
 
 In the face of mounting criticism over its handling of the situation, Malaysia Airlines has defended its actions, saying it took time to verify satellite signals and give authorities a chance to analyze their significance before releasing information. 
 
 But at Sunday's Beijing briefing, a majority of the people in the room stood up when the man asked how many had lost trust in the airline and the Malaysian government. 
 
 Another man rushed the front of the room and tried to throw a punch but was stopped. 
 
 The airline has been picking up the tab for families of the Chinese passengers to stay in Beijing during the ordeal. 
 
 China is sending technical experts to join the investigation, and two Chinese search vessels headed for the Strait of Malacca, according to Xinhua. 
 
 People are across the world have shown their support for those involved. 
 
 During his weekly Sunday message following prayers at the Vatican, Pope Francis asked the crowd to pray for the crew members and passengers of the missing Malaysia Airlines plane and their families. "We are close to them in this difficult moment," Pope Francis said. ||||| Story highlights Japan to join 8 other nations in search, ministry says 
 
 Plane's transponder had stopped, Malaysian Air Force official says 
 
 Missing flight was way off course, heading in wrong direction, official says 
 
 Experts unsure on what caused transponder to go off, what it means for plane 
 
 It was 1:30 a.m. when Malaysia Airlines Flight 370 lost all communications, including important transponder signals that send data on altitude, direction and speed. Still, it showed up on radar for about 1 hour, 10 minutes longer -- until it vanished, having apparently moved away from its intended destination, hundreds of miles off course. 
 
 Those details -- told to CNN by a senior Malaysian air force official, who declined to be named because he is not authorized to speak to the media -- seemingly shed more light on what happened to the aircraft that mysteriously went missing early Saturday. 
 
 But if these assertions are true -- and other reports, citing a different Malaysian official, cast doubt on them -- many big questions remain. Why were the communications lost? Why was the Boeing 777 going the direction it was? And where did it end up? 
 
 "Something happened to that airplane, that was obviously out of the norm, that caused it to depart from its normal flight path," said Mark Weiss, a former 777 pilot now with the Washington-based Spectrum Group consulting firm. "... It's difficult not to speculate." 
 
 Peter Goelz, former managing director of the National Transportation Safety Board, thinks all this information -- if correct -- ominously suggests that someone purposefully cut off the transponder and steered the plane from its intended destination. 
 
 "This kind of deviation in course is simply inexplicable," said Goelz. 
 
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 Other experts aren't convinced that there were bad actors -- be they hijackers or an ill-intentioned crew member. They say there could have been some sort of sudden catastrophic electronic failure or more that spurred the crew to try to turn around, with no luck. 
 
 "Perhaps there was a power problem," said veteran pilot Kit Darby, former president of Aviation Information Resources, adding that backup power systems would only last about an hour. "(It is) natural for the pilot, in my view, to return to where he knows the airports." 
 
 Still, while they have theories, even those who have piloted massive commercial airliners like this one admit that they can't conclude anything until the plane is found. For now, the massive multinational search has yielded no breakthrough -- which has only added to the heartache for the friends and family of the 239 passengers and crew on board. 
 
 The Malaysian air force official's revelations may provide more direction, though clarity and closure are still elusive. 
 
 "There are still as many possibilities out there, maybe more, now that we know about the transponders being off and the length of time that plane flew in the air without them," said CNN law enforcement analyst Tom Fuentes. "It still leaves mechanical, terrorism (and) other issues as much in the air as they were before." 
 
 Intentional or catastrophic mechanical failure? 
 
 According to the Malaysian air force official, the plane's transponder apparently stopped working at about the time flight controllers lost contact with it, near the coast of Vietnam. 
 
 The air force eventually and totally lost track of the plane over Pulau Perak, a tiny island in the Strait of Malacca -- many hundreds of miles from the usual flight path for aircraft traveling between Kuala Lumpur and Beijing, the official said. 
 
 If the data cited by the source is correct, the aircraft was flying away from Beijing and on the opposite side of the Malay Peninsula from its scheduled route. 
 
 Why would the transponder -- an electrical instrument in commercial airline cockpits that continuously transmits information such as altitude, location, direction and speed -- have gone off? 
 
 Goelz, the former NTSB managing director, and others point out the only reason for someone to intentionally turn off the transponder is to conceal the plane's location and direction. Someone with nefarious intentions of taking over an aircraft and steering it to where it wasn't supposed to be -- or perhaps planning on crashing it -- might do just that. 
 
 "You have to have a very deliberate process to turn the transponder off," he said. "... There might still be mechanical explanations on what was going on, but those mechanical explanations are narrowing quickly." 
 
 Anthony Roman, a trained pilot and consultant, said that a fast-moving fire might have moved through the cockpit and rendered everything, including the crew, effectively powerless to do much more than turn the plane around. 
 
 "Fires are insidious," Roman told CNN's Wolf Blitzer. "They can happen quickly and knock out multiple systems quickly." 
 
 Darby, for one, believes purely mechanical issues remain the most valid possibility now. His main point is: "Everything is electrical." In other words, if there's some sort of "catastrophic failure" for whatever reason, that could knock out systems like the transponder. 
 
 If that would happen, the plane could fly for some time without electricity but not indefinitely. Any attempts to steer it would be harder in the dark without functioning flight instruments said Darby, a retired United captain. 
 
 Whether the air force official's account is true, that possibility and others make the mystery more and more confounding. 
 
 Photos: The search for MH370 Photos: The search for MH370 Two years after Malaysia Airlines Flight 370 went missing, a relative of one of the passengers burns incense in Beijing on March 8, 2016. Flight 370 vanished on March 8, 2014, as it flew from Kuala Lumpur, Malaysia, to Beijing. There were 239 people on board. Hide Caption 1 of 43 Photos: The search for MH370 On July 29, police carry a piece of debris on Reunion Island, a French territory in the Indian Ocean. A week later, authorities confirmed that the debris was from the missing flight. Hide Caption 2 of 43 Photos: The search for MH370 Staff members with the Australian Transport Safety Bureau examine a piece of aircraft debris at their laboratory in Canberra, Australia, on July 20. The flap was found in June by residents on Pemba Island off the coast of Tanzania, and officials had said it was highly likely to have come from Flight 370. Experts at the Australian Transport Safety Bureau, which is heading up the search for the plane, confirmed that the part was indeed from the missing aircraft. Hide Caption 3 of 43 Photos: The search for MH370 In late February, American tourist Blaine Gibson found a piece of plane debris off Mozambique, a discovery that renewed hope of solving the mystery of the missing flight. The piece measured 35 inches by 22 inches. A U.S. official said it was likely the wreckage came from a Boeing 777, which MH370 was. Hide Caption 4 of 43 Photos: The search for MH370 Relatives of the flight's passengers console each other outside the Malaysia Airlines office in Subang, Malaysia, on February 12, 2015. Protesters had demanded that the airline withdraw the statement that all 239 people aboard the plane were dead. Hide Caption 5 of 43 Photos: The search for MH370 A police officer watches a couple cry outside the airline's office building in Beijing after officials refused to meet with them on June 11, 2014. The couple's son was on the plane. Hide Caption 6 of 43 Photos: The search for MH370 Members of the media scramble to speak with Azharuddin Abdul Rahman, director general of Malaysia's Civil Aviation Department, at a hotel in Kuala Lumpur, Malaysia, on May 27, 2014. Data from communications between satellites and the missing flight was released the day before, more than two months after relatives of passengers said they requested it be made public. Hide Caption 7 of 43 Photos: The search for MH370 Operators aboard the Australian ship Ocean Shield move Bluefin-21, the U.S. Navy's autonomous underwater vehicle, into position to search for the jet on April 14, 2014. Hide Caption 8 of 43 Photos: The search for MH370 A member of the Royal New Zealand Air Force looks out of a window while searching for debris off the coast of western Australia on April 13, 2014. Hide Caption 9 of 43 Photos: The search for MH370 The HMS Echo, a vessel with the British Roya; Navy, moves through the waters of the southern Indian Ocean on April 12, 2014. Hide Caption 10 of 43 Photos: The search for MH370 A Royal Australian Air Force AP-3C Orion, on a mission to drop sonar buoys to assist in the search, flies past the Australian vessel Ocean Shield on April 9, 2014. Hide Caption 11 of 43 Photos: The search for MH370 A relative of a missing passenger cries at a vigil in Beijing on April 8, 2014. Hide Caption 12 of 43 Photos: The search for MH370 Australian Defense Force divers scan the water for debris in the southern Indian Ocean on April 7, 2014. Hide Caption 13 of 43 Photos: The search for MH370 A towed pinger locator is readied to be deployed off the deck of the Australian vessel Ocean Shield on April 7, 2014. Hide Caption 14 of 43 Photos: The search for MH370 A member of the Royal New Zealand Air Force looks at a flare in the Indian Ocean during search operations on April 4, 2014. Hide Caption 15 of 43 Photos: The search for MH370 On March 30, 2014, a woman in Kuala Lumpur prepares for an event in honor of those aboard Flight 370. Hide Caption 16 of 43 Photos: The search for MH370 The sole representative for the families of Flight 370 passengers leaves a conference at a Beijing hotel on March 28, 2014, after other relatives left en masse to protest the Malaysian government's response to their questions. Hide Caption 17 of 43 Photos: The search for MH370 A member of the Royal Australian Air Force is silhouetted against the southern Indian Ocean during the search for the missing jet on March 27, 2014. Hide Caption 18 of 43 Photos: The search for MH370 Flight Lt. Jayson Nichols looks at a map aboard a Royal Australian Air Force aircraft during a search on March 27, 2014. Hide Caption 19 of 43 Photos: The search for MH370 People in Kuala Lumpur light candles during a ceremony held for the missing flight's passengers on March 27, 2014. Hide Caption 20 of 43 Photos: The search for MH370 Malaysian Prime Minister Najib Razak, center, delivers a statement about the flight on March 24, 2014. Razak's announcement came after the airline sent a text message to relatives saying it "deeply regrets that we have to assume beyond any reasonable doubt that MH 370 has been lost and that none of those onboard survived." Hide Caption 21 of 43 Photos: The search for MH370 Grieving relatives of missing passengers leave a hotel in Beijing on March 24, 2014. Hide Caption 22 of 43 Photos: The search for MH370 A passenger views a weather map in the departures terminal of Kuala Lumpur International Airport on March 22, 2014. Hide Caption 23 of 43 Photos: The search for MH370 A Chinese satellite captured this image, released on March 22, 2014, of a floating object in the Indian Ocean, according to China's State Administration of Science. It was a possible lead in the search for the missing plane. Surveillance planes were looking for two objects spotted by satellite imagery in remote, treacherous waters more than 1,400 miles from the west coast of Australia. Hide Caption 24 of 43 Photos: The search for MH370 Satellite imagery provided by the Australian Maritime Safety Authority on March 20, 2014, showed debris in the southern Indian Ocean that could have been from Flight 370. The announcement by Australian officials raised hopes of a breakthrough in the frustrating search. Hide Caption 25 of 43 Photos: The search for MH370 Another satellite shot provided by the Australian Maritime Safety Authority shows possible debris from the flight. Hide Caption 26 of 43 Photos: The search for MH370 A distraught relative of a missing passenger breaks down while talking to reporters at Kuala Lumpur International Airport on March 19, 2014. Hide Caption 27 of 43 Photos: The search for MH370 On March 18, 2014, a relative of a missing passenger tells reporters in Beijing about a hunger strike to protest authorities' handling of information about the missing jet. Hide Caption 28 of 43 Photos: The search for MH370 U.S. Navy crew members assist in search-and-rescue operations in the Indian Ocean on March 16, 2014. Hide Caption 29 of 43 Photos: The search for MH370 Members of the Chinese navy continue search operations on March 13, 2014. After starting in the sea between Malaysia and Vietnam, the plane's last confirmed location, search efforts expanded west into the Indian Ocean. Hide Caption 30 of 43 Photos: The search for MH370 A Vietnamese military official looks out an aircraft window during search operations March 13, 2014. Hide Caption 31 of 43 Photos: The search for MH370 Malaysian air force members look for debris near Kuala Lumpur on March 13, 2014. Hide Caption 32 of 43 Photos: The search for MH370 Relatives of missing passengers wait for the latest news at a hotel in Beijing on March 12, 2014. Hide Caption 33 of 43 Photos: The search for MH370 A member of the Vietnamese air force checks a map while searching for the missing plane on March 11, 2014. Hide Caption 34 of 43 Photos: The search for MH370 A Vietnamese air force plane found traces of oil that authorities had suspected to be from the missing Malaysia Airlines plane, the Vietnamese government online newspaper reported on March 8, 2014. However, a sample from the slick showed it was bunker oil, typically used to power large cargo ships, Malaysia's state news agency, Bernama, reported on March 10, 2014. Hide Caption 35 of 43 Photos: The search for MH370 A U.S. Navy Seahawk helicopter lands aboard the USS Pinckney to change crews on March 9, 2014, before returning to search for the missing plane in the Gulf of Thailand. Hide Caption 36 of 43 Photos: The search for MH370 Buddhist monks at Kuala Lumpur International Airport offer a special prayer for the missing passengers on March 9, 2014. Hide Caption 37 of 43 Photos: The search for MH370 Members of a Chinese emergency response team board a rescue vessel at the port of Sanya in China's Hainan province on March 9, 2014. Hide Caption 38 of 43 Photos: The search for MH370 The rescue vessel sets out from Sanya in the South China Sea on March 9, 2014. Hide Caption 39 of 43 Photos: The search for MH370 Malaysian Prime Minister Najib Razak, center, arrives to meet family members of missing passengers at the reception center at Kuala Lumpur International Airport on March 8, 2014. Hide Caption 40 of 43 Photos: The search for MH370 A relative of two missing passengers reacts at their home in Kuala Lumpur on March 8, 2014. Hide Caption 41 of 43 Photos: The search for MH370 Chinese police at the Beijing airport stand beside the arrival board showing delayed Flight 370 in red on March 8, 2014. Hide Caption 42 of 43 Photos: The search for MH370 Malaysia Airlines Group CEO Ahmad Juahari Yahya, front, speaks during a news conference at a hotel in Sepang on March 8, 2014. "We deeply regret that we have lost all contacts" with the jet, he said. Hide Caption 43 of 43 
 
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 "You couldn't make this story up," said Michael Goldfarb, a former official with the Federal Aviation Administration. 
 
 Terrorism a possibility 
 
 Authorities have said they're looking at all possibilities to explain what happened to the Malaysia Airlines aircraft. 
 
 Earlier Tuesday, the head of the international police organization Interpol said that his agency increasingly believed the incident was not related to terrorism. 
 
 "The more information we get, the more we're inclined to conclude that it was not a terrorist incident," Interpol Secretary General Ronald Noble said at a news conference in Lyon, France. 
 
 Yet -- speaking Tuesday about what he called a "very disturbing mystery" -- CIA Director John Brennan insisted terrorism remains a possibility. 
 
 "I don't know (what happened)," he said. "But I don't think people should, at this point, rule out any of these lines of inquiry." 
 
 The two passengers who have dominated headlines the last two days entered Malaysia using valid Iranian passports, Noble said. But they used stolen Austrian and Italian passports to board the missing Malaysian plane, he said. 
 
 Noble gave their names and ages as Pouri Nourmohammadi, 18, and Delavar Seyed Mohammad Reza, 29. 
 
 Malaysian police had earlier identified Nourmohammadi, using a slightly different name and age, and said they believed he was trying to migrate to Germany. 
 
 Inspector General Khalid Abu Bakar of the Royal Malaysian Police said it doesn't appear the younger Iranian posed a threat. 
 
 "We have been checking his background," Khalid said, noting "other police organizations" have been consulted. "And we believe that he is not likely to be a member of any terrorist group," Khalid said. 
 
 After he failed to arrive in Frankfurt, the final destination of his ticket, his mother contacted authorities, Khalid said. According to ticketing records, the ticket to Frankfurt was booked under the stolen Austrian passport. 
 
 Extensive search for plane 
 
 No one knows where these two men and the other 237 people on the plane ended up. Every lead that has raised hopes of tracing the commercial jet has so far petered out. 
 
 Over the past few days, search teams have been scouring tens of thousands of square miles of sea between the northeast coast of Malaysia and southwest Vietnam. They have also been searching off the west coast of the Malay Peninsula, in the Strait of Malacca, and north into the Andaman Sea. 
 
 The search also encompasses the land in between the two areas of sea. 
 
 But it could be days, weeks or even months before the searchers find anything that begins to explain what happened to the plane, which disappeared early Saturday en route to Beijing. 
 
 In the case of Air France Flight 447, which disappeared over the Atlantic in 2009, it took five days just to find the first floating wreckage. 
 
 And it was nearly two years before investigators found the bulk of the French plane's wreckage and the majority of the bodies of the 228 people on board, about 12,000 feet below the surface of the ocean. 
 
 The Gulf of Thailand, the area where the missing Malaysian plane was last detected, is much shallower, with a maximum depth of only 260 feet and an average depth of about 150 feet. 
 
 Still, they have to find it first. The newly disclosed revelation about the plane's direction doesn't help, as it means less certainty and more time for currents to move the wreckage around. 
 
 "Crucial time is passing," David Gallo, with the Woods Hole Oceanographic Institution, told CNN's Wolf Blitzer on Monday. "That search area -- that haystack -- is getting bigger and bigger and bigger." 
 
 Thailand, Singapore, Indonesia, Vietnam, Australia, the United States, China and Malaysia are all taking part in the search, White House spokesman Jay Carney said. Japan has also dispatched a team to the area, with Japanese military and coast guard crews likely to follow, its foreign ministry announced Wednesday. 
 
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 That helps takes all forms, such as many as 10 Chinese satellites monitoring the area to the helicopters ready-to-dispatch off of U.S. warships. 
 
 CNN aviation correspondent Richard Quest described the search as "extremely painstaking work," suggesting a grid would have been drawn over the ocean for teams to comb, bit by bit. 
 
 Quest said that the expanding search area shows how little idea rescue officials have of where the plane might be. But he's still confident they'll find it eventually. 
 
 "It's not hopeless, by any means. They will find it," he said. "They have to. They have to know what happened." 
 
 Until they do, patience is growing thin for friends and family members of those aboard Flight 370. 
 
 As a middle-aged man -- the father of one such passenger -- shouted Tuesday at an airline agent in Beijing: "Time is passing by." ||||| Story highlights The search area for the plane covers sea and land, including 11 countries 
 
 The plane's pilots are a main investigation focus 
 
 Details have emerged about some key moments during the flight 
 
 As investigators search for clues to unravel the mystery of where Malaysia Airlines Flight 370 went, there were several key developments over the weekend. 
 
 But major questions still remain. 
 
 Here's a cheat sheet to help you get up to speed on the latest developments: 
 
 Where are investigators searching now? 
 
 The search has expanded to cover large swaths of land and sea , including 11 countries and deep oceans. Where the plane went is anybody's guess. As 26 nations help try to find the missing plane, there's also a process of elimination in which investigators try to piece together where the aircraft isn't. Pakistan said Sunday that the plane never showed up on its civilian radars and would have been treated as a threat if it had. The Times of India reported that India's military also said there was no way the plane could have flown over India without being picked up on radar. 
 
 What's one main focus of the investigation? 
 
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 Malaysia's Prime Minister has said that somebody deliberately steered the plane off course. That means the pilots have become one obvious focus for investigators . On Sunday, Malaysian police said they were still investigating a flight simulator seized from pilot Zaharie Ahmad Shah's home. Peter Chong, a friend of the 53-year-old pilot's, said it's unfair to imply that Zaharie had anything to do with what happened to the plane. He said he'd been to Zaharie's house and tried out the flight simulator. "It's a reflection of his love for people," Chong said, "because he wants to share the joy of flying with his friends." 
 
 A 29-year-old Malaysian civil aviation engineer, Mohammed Khairul Amri Selamat, who works for a private jet charter company, was on the flight. Police are investigating all passengers and crew, but he is likely to be of particular interest because of his aviation knowledge. "I am confident that he is not involved," his father said. "They're welcome to investigate me and my family." 
 
 What do we know about key moments on the flight? 
 
 For days, we've been talking about the last transponder signal the plane sent. And now it appears another system that sends data about the plane, the Aircraft Communications Addressing and Reporting System, was shut off, too . Authorities say the last transmission from that system came early in the flight, at 1:07 a.m. But they say they don't know exactly when the system was shut down, as the next transmission wasn't due until 1:37 a.m. Someone inside the cockpit, believed to be the co-pilot, made the plane's last verbal communication with air traffic controllers at 1:19 a.m., saying, "All right, good night." The transponder was then switched off at 1:21 a.m., authorities say, and all civilian radar lost contact with the plane altogether about 1:30 a.m. Military radar last detected the plane at 2:15 a.m. off Malaysia's west coast, hundreds of miles off course. And at 8:11 a.m., more than seven hours after takeoff, a satellite made the last electronic connection, known as a "handshake," with the plane. 
 
 Though some details have come into focus, major questions remain unanswered: 
 
 Where's the plane? 
 
 Satellite and radar data have given authorities some clues but not enough to pinpoint the plane. Right now, investigators are focusing on two corridors where the plane might have either crashed or landed: a northern arc that stretches from the border of Kazakhstan and Turkmenistan in central Asia to northern Thailand, and a southern arc that spans from Indonesia to the southern Indian Ocean. Because the northern parts of the traffic corridor include some tightly guarded airspace over India, Pakistan and even some U.S. installations in Afghanistan, U.S. authorities believe it's more likely the aircraft crashed into waters outside of the reach of radar south of India, a U.S. official told CNN. If it had flown farther north, it's likely it would have been detected by radar. However, on Monday, an Indian military official told CNN that its military radar in the area of the Andaman and Nicobar Islands isn't as closely watched as it is in other areas. This leaves open the possibility that the flight may not have been picked up by Indian military radar around the time of its last believed Malaysian radar contact, near the island of Pulau Perak in the Strait of Malacca. 
 
 Who would deliberately divert it? 
 
 Photos: The search for MH370 Photos: The search for MH370 Two years after Malaysia Airlines Flight 370 went missing, a relative of one of the passengers burns incense in Beijing on March 8, 2016. Flight 370 vanished on March 8, 2014, as it flew from Kuala Lumpur, Malaysia, to Beijing. There were 239 people on board. Hide Caption 1 of 43 Photos: The search for MH370 On July 29, police carry a piece of debris on Reunion Island, a French territory in the Indian Ocean. A week later, authorities confirmed that the debris was from the missing flight. Hide Caption 2 of 43 Photos: The search for MH370 Staff members with the Australian Transport Safety Bureau examine a piece of aircraft debris at their laboratory in Canberra, Australia, on July 20. The flap was found in June by residents on Pemba Island off the coast of Tanzania, and officials had said it was highly likely to have come from Flight 370. Experts at the Australian Transport Safety Bureau, which is heading up the search for the plane, confirmed that the part was indeed from the missing aircraft. Hide Caption 3 of 43 Photos: The search for MH370 In late February, American tourist Blaine Gibson found a piece of plane debris off Mozambique, a discovery that renewed hope of solving the mystery of the missing flight. The piece measured 35 inches by 22 inches. A U.S. official said it was likely the wreckage came from a Boeing 777, which MH370 was. Hide Caption 4 of 43 Photos: The search for MH370 Relatives of the flight's passengers console each other outside the Malaysia Airlines office in Subang, Malaysia, on February 12, 2015. Protesters had demanded that the airline withdraw the statement that all 239 people aboard the plane were dead. Hide Caption 5 of 43 Photos: The search for MH370 A police officer watches a couple cry outside the airline's office building in Beijing after officials refused to meet with them on June 11, 2014. The couple's son was on the plane. Hide Caption 6 of 43 Photos: The search for MH370 Members of the media scramble to speak with Azharuddin Abdul Rahman, director general of Malaysia's Civil Aviation Department, at a hotel in Kuala Lumpur, Malaysia, on May 27, 2014. Data from communications between satellites and the missing flight was released the day before, more than two months after relatives of passengers said they requested it be made public. Hide Caption 7 of 43 Photos: The search for MH370 Operators aboard the Australian ship Ocean Shield move Bluefin-21, the U.S. Navy's autonomous underwater vehicle, into position to search for the jet on April 14, 2014. Hide Caption 8 of 43 Photos: The search for MH370 A member of the Royal New Zealand Air Force looks out of a window while searching for debris off the coast of western Australia on April 13, 2014. Hide Caption 9 of 43 Photos: The search for MH370 The HMS Echo, a vessel with the British Roya; Navy, moves through the waters of the southern Indian Ocean on April 12, 2014. Hide Caption 10 of 43 Photos: The search for MH370 A Royal Australian Air Force AP-3C Orion, on a mission to drop sonar buoys to assist in the search, flies past the Australian vessel Ocean Shield on April 9, 2014. Hide Caption 11 of 43 Photos: The search for MH370 A relative of a missing passenger cries at a vigil in Beijing on April 8, 2014. Hide Caption 12 of 43 Photos: The search for MH370 Australian Defense Force divers scan the water for debris in the southern Indian Ocean on April 7, 2014. Hide Caption 13 of 43 Photos: The search for MH370 A towed pinger locator is readied to be deployed off the deck of the Australian vessel Ocean Shield on April 7, 2014. Hide Caption 14 of 43 Photos: The search for MH370 A member of the Royal New Zealand Air Force looks at a flare in the Indian Ocean during search operations on April 4, 2014. Hide Caption 15 of 43 Photos: The search for MH370 On March 30, 2014, a woman in Kuala Lumpur prepares for an event in honor of those aboard Flight 370. Hide Caption 16 of 43 Photos: The search for MH370 The sole representative for the families of Flight 370 passengers leaves a conference at a Beijing hotel on March 28, 2014, after other relatives left en masse to protest the Malaysian government's response to their questions. Hide Caption 17 of 43 Photos: The search for MH370 A member of the Royal Australian Air Force is silhouetted against the southern Indian Ocean during the search for the missing jet on March 27, 2014. Hide Caption 18 of 43 Photos: The search for MH370 Flight Lt. Jayson Nichols looks at a map aboard a Royal Australian Air Force aircraft during a search on March 27, 2014. Hide Caption 19 of 43 Photos: The search for MH370 People in Kuala Lumpur light candles during a ceremony held for the missing flight's passengers on March 27, 2014. Hide Caption 20 of 43 Photos: The search for MH370 Malaysian Prime Minister Najib Razak, center, delivers a statement about the flight on March 24, 2014. Razak's announcement came after the airline sent a text message to relatives saying it "deeply regrets that we have to assume beyond any reasonable doubt that MH 370 has been lost and that none of those onboard survived." Hide Caption 21 of 43 Photos: The search for MH370 Grieving relatives of missing passengers leave a hotel in Beijing on March 24, 2014. Hide Caption 22 of 43 Photos: The search for MH370 A passenger views a weather map in the departures terminal of Kuala Lumpur International Airport on March 22, 2014. Hide Caption 23 of 43 Photos: The search for MH370 A Chinese satellite captured this image, released on March 22, 2014, of a floating object in the Indian Ocean, according to China's State Administration of Science. It was a possible lead in the search for the missing plane. Surveillance planes were looking for two objects spotted by satellite imagery in remote, treacherous waters more than 1,400 miles from the west coast of Australia. Hide Caption 24 of 43 Photos: The search for MH370 Satellite imagery provided by the Australian Maritime Safety Authority on March 20, 2014, showed debris in the southern Indian Ocean that could have been from Flight 370. The announcement by Australian officials raised hopes of a breakthrough in the frustrating search. Hide Caption 25 of 43 Photos: The search for MH370 Another satellite shot provided by the Australian Maritime Safety Authority shows possible debris from the flight. Hide Caption 26 of 43 Photos: The search for MH370 A distraught relative of a missing passenger breaks down while talking to reporters at Kuala Lumpur International Airport on March 19, 2014. Hide Caption 27 of 43 Photos: The search for MH370 On March 18, 2014, a relative of a missing passenger tells reporters in Beijing about a hunger strike to protest authorities' handling of information about the missing jet. Hide Caption 28 of 43 Photos: The search for MH370 U.S. Navy crew members assist in search-and-rescue operations in the Indian Ocean on March 16, 2014. Hide Caption 29 of 43 Photos: The search for MH370 Members of the Chinese navy continue search operations on March 13, 2014. After starting in the sea between Malaysia and Vietnam, the plane's last confirmed location, search efforts expanded west into the Indian Ocean. Hide Caption 30 of 43 Photos: The search for MH370 A Vietnamese military official looks out an aircraft window during search operations March 13, 2014. Hide Caption 31 of 43 Photos: The search for MH370 Malaysian air force members look for debris near Kuala Lumpur on March 13, 2014. Hide Caption 32 of 43 Photos: The search for MH370 Relatives of missing passengers wait for the latest news at a hotel in Beijing on March 12, 2014. Hide Caption 33 of 43 Photos: The search for MH370 A member of the Vietnamese air force checks a map while searching for the missing plane on March 11, 2014. Hide Caption 34 of 43 Photos: The search for MH370 A Vietnamese air force plane found traces of oil that authorities had suspected to be from the missing Malaysia Airlines plane, the Vietnamese government online newspaper reported on March 8, 2014. However, a sample from the slick showed it was bunker oil, typically used to power large cargo ships, Malaysia's state news agency, Bernama, reported on March 10, 2014. Hide Caption 35 of 43 Photos: The search for MH370 A U.S. Navy Seahawk helicopter lands aboard the USS Pinckney to change crews on March 9, 2014, before returning to search for the missing plane in the Gulf of Thailand. Hide Caption 36 of 43 Photos: The search for MH370 Buddhist monks at Kuala Lumpur International Airport offer a special prayer for the missing passengers on March 9, 2014. Hide Caption 37 of 43 Photos: The search for MH370 Members of a Chinese emergency response team board a rescue vessel at the port of Sanya in China's Hainan province on March 9, 2014. Hide Caption 38 of 43 Photos: The search for MH370 The rescue vessel sets out from Sanya in the South China Sea on March 9, 2014. Hide Caption 39 of 43 Photos: The search for MH370 Malaysian Prime Minister Najib Razak, center, arrives to meet family members of missing passengers at the reception center at Kuala Lumpur International Airport on March 8, 2014. Hide Caption 40 of 43 Photos: The search for MH370 A relative of two missing passengers reacts at their home in Kuala Lumpur on March 8, 2014. Hide Caption 41 of 43 Photos: The search for MH370 Chinese police at the Beijing airport stand beside the arrival board showing delayed Flight 370 in red on March 8, 2014. Hide Caption 42 of 43 Photos: The search for MH370 Malaysia Airlines Group CEO Ahmad Juahari Yahya, front, speaks during a news conference at a hotel in Sepang on March 8, 2014. "We deeply regret that we have lost all contacts" with the jet, he said. Hide Caption 43 of 43 
 
 JUST WATCHED The search for Flight 370 continues Replay More Videos ... MUST WATCH The search for Flight 370 continues 02:47 
 
 JUST WATCHED Will mystery of Flight 370 be solved? Replay More Videos ... MUST WATCH Will mystery of Flight 370 be solved? 05:09 
 
 In addition to the pilots, other passengers and crew members on board the plane, as well as any ground staff who came into contact with it, are under investigation. The bottom line, investigators say, is that whoever flew the plane off course for hours appeared to know what they were doing. Investigators are looking into the backgrounds of the passengers to see whether any of them were trained pilots. "There are still a few countries who have yet to respond to our request for a background check," said Khalid Abu Bakar, inspector general of the Royal Malaysian Police Force. "But there are a few ... foreign intelligence agencies who have cleared all the(ir) passengers." 
 
 Why would they do it, and how? 
 
 Finding a motive behind the plane's disappearance is a key problem investigators must solve. They haven't released any concrete details. Speculation has surged about the possibility of terrorism or hijacking, but that hasn't been confirmed. 
 
 Is there any chance the passengers and crew survived? 
 
 It's possible the plane's last satellite contact could have been made from the ground, as long as the airplane still had electrical power, Malaysia's civil aviation chief Azharuddin Abdul Rahman said Sunday. For the families and loved ones of those aboard Flight 370, some find comfort that there's no evidence the plane crashed. The father of one passenger, who watched updates from Malaysia in a Beijing hotel, said he hoped the plane was hijacked because that gave him reason to think his son had survived. "I hope they are alive," he said , "no matter how small the chance is." 
 
 Does the possibility that the plane is on land change anything about the investigation? 
 
 Yes, analysts said. It means it's even more pressing that authorities find the plane. "Time is even more of the essence. If this airplane has been taken to be used as a weapon, then the time that has been taken to prepare the aircraft for whatever deed is the plan -- obviously, to thwart that, it's all about time," said Shawn Pruchnicki, who teaches aviation safety and accident investigation at Ohio State University. CNN aviation analyst Jim Tilmon, a former American Airlines pilot, said that whoever deliberately steered the plane off course probably did it with help. But what's next is anyone's guess, he said. "We have been behind them all along," he said. "So now, if they had a plan, and if that plan included being able to set down someplace and refuel a little bit, we are looking at something that we may never see the end of." 
 
 Report: Plane flew low to avoid radar 
 
 Malaysian officials on Monday denied knowledge of a newspaper report that the plane may have dropped to an altitude of 5,000 feet to defeat commercial radar coverage. "We are not aware of that report, and that's a thing the investigative team has to look into. It does not come from us," Malaysia Airlines CEO Ahmad Jauhari Yahya told reporters in Kuala Lumpur. CNN could not immediately confirm the newspaper's account.
– The echo chamber that is the search for Malaysia Airlines Flight 370 has yet to yield much in the way of definites, but the focus continues to remain on the pilots and the theory that the jet's disappearance was not an accident or mechanical failure. This "was an intentional, deliberate act to bring down this airplane," House Homeland Security chief Michael McCaul said today. "Something was going on with the pilot. This all leads toward the cockpit." Former NTSB managing director Peter Goelz seconded that, reports Politico, saying that the intentional shuttering of the plane's communications equipment "is damning evidence that indicates something was going on in the flight deck." Meanwhile, House Intel chair Mike Rogers wants to know "if there was some terrorist nexus" involved, adding that while many theories on the plane's fate abound, it "still may be at the bottom of the Indian Ocean." A look around at the latest: The AP delves into the relatively rare occurrence of pilot suicide, which was a factor in .3% of plane crashes in the decade ending in 2012. The possibility that the plane was hijacked has given hope to some passengers' families, reports the LA Times. "My gut feeling is that it landed. I still feel his spirit. I don’t feel he is dead," says the partner of American passenger Philip Wood. Pakistan says the plane never registered on its radar, reports CNN—and if it had, it would have been treated as a terrorist threat. India today called off search efforts for the jet pending "a strategy for further searches" from Malaysian officials, reports the AP. Slate runs down the 634 runways where the missing plane could have landed.