KUALA LUMPUR, March 21 (Reuters) - If two blurred objects photographed from space are confirmed as debris from Flight MH370, scientists will still face a daunting task to find and recover the sensitive recorders containing clues to the Malaysian jet's disappearance. 
 
 With so little known about why the Beijing-bound Malaysia Airlines flight changed course and disappeared after leaving Kuala Lumpur on March 8, finding the 'black boxes' is seen as the only real hope of understanding what happened to the plane and the 239 people on board. 
 
 Australian Prime Minister Tony Abbott on Thursday said objects possibly belonging to the plane had been discovered in the Indian Ocean. The area is around 2,500 km (1,500 miles) southwest of Perth, above a volcanic ridge in waters estimated to be 2,500 to 4,000 metres (8,200 to 13,120 feet) deep. 
 
 It roughly corresponds to the far end of a southern track the aircraft could have taken after investigators suspect it was deliberately diverted. 
 
 "It can be incredibly rough and difficult. It can be very windy with strong currents, though it can equally be calm," said David Gallo, director of special projects at the Woods Hole Oceanographic Institution (WHOI) in Falmouth, Massachusetts, referring to the general area where the objects were seen. 
 
 Flight MH370's disappearance has been compared to the 2009 Air France jet disaster, which puzzled investigators until a mission led by WHOI found the black boxes in 3,900 metres (12,800 feet) of water. 
 
 But whereas investigators knew roughly where Flight AF447 had hit the Atlantic Ocean on a stormy night in June 2009, search crews know much less about where the Malaysian jet ended up, including whether or where it ran out of fuel. 
 
 "If it is confirmed as debris, then the first priority is to recover and record each piece and see how high or low it is sitting in the water. This may help indicate how it has been moved by currents and winds," said Gallo, who took part in the Air France search. 
 
 DEBRIS COULD HAVE MOVED 
 
 The immediate problem will be to find the debris, which may have moved since the satellite images were taken on March 16. 
 
 It could take several days to verify the satellite lead, a source close to the investigation said. Military aircraft from Australia, the United States and New Zealand have so far found nothing during a search hampered by strong winds and rain. Neither has a merchant ship in the area. 
 
 If the objects - the biggest measures up to 24 metres (79 feet) - are from the Boeing 777, recovery teams will work as quickly as possible to locate the rest of the wreckage in the hope it leads them to the data and cockpit voice recorders. 
 
 To do this, scientists have developed computer models to effectively play waves and winds backwards, allowing rescue workers to retrace the movements of debris to the site of a crash. 
 
 "There are sophisticated models that allow you to work backwards from the current position of each piece of debris, after considering the currents and the winds and so on," said Gallo. 
 
 "That enables you to say X marks the spot on the surface." 
 
 Investigators hope such recent developments in oceanography will help shed light on the baffling disappearance of Flight MH370. 
 
 But not all experts agree computer simulations will easily replace the gruelling routine of searching from the air and the sea. 
 
 Although research has continued since the Air France jet ploughed into the Atlantic, a detailed annex to the report on that disaster, which was blamed mainly on pilot error, raised questions in 2012 over the consistency of such "retro-drift" calculations. 
 
 For example, when the French Navy dropped special buoys at the same spot a year after the crash they scattered hundreds of miles apart, highlighting the turbulence of ocean currents. 
 
 RACE AGAINST TIME 
 
 If the report of suspected debris is confirmed, naval vessels will also drag a sonar through the water to seek the black boxes through radio beacons, but time for this is running out. 
 
 The black boxes are designed to have a battery life of at least 30 days, leaving possibly only 17 days to locate them before the signals die. 
 
 But for every knot, or nautical mile per hour, of current in the rough waters of the southern Indian Ocean, an object could theoretically float for 312 miles (500 km) in 13 days, the time the Malaysian plane has been missing. 
 
 That could present investigators with a much larger potential search area than the 40-mile radius for AF447. 
 
 In 2012, France's BEA air crash investigation agency recommended in its report on the Air France disaster that the battery life on locator beacons be increased to 90 days. 
 
 Although this has been backed by global regulators, it will not become mandatory until towards the end of the decade. 
 
 Other proposals that could potentially make it easier to find MH370 remain bogged down in talks between regulators and the aviation industry, with no timetable for putting them into effect, Reuters reported last week. 
 
 These include adding a new frequency for the beacons so that their signals travel further and can more easily be heard by military ships lacking specialist air crash recovery equipment. 
 
 Existing signals travel about 2,000 to 3,000 metres (6,560 to 9,840 feet) under water, according to the French sea search annex, whereas the area now being combed for debris is up to 4,000 metres deep. 
 
 To close this gap, search teams would bring in boats capable of carrying several miles of cables to drag sonars at lower depths, but experts note moving them into place can take time. 
 
 If by the end of 30 days nothing is found, the search could rely on remote underwater vehicles to scour the seabed. 
 
 To find the Air France wreckage, WHOI used remote-operated REMUS underwater vehicles developed by the U.S. Navy. 
 
 "It was the biggest use of deep-ocean firepower in one spot," Gallo said. (Editing by Dean Yates) ||||| 1 of 12. Lieutenant Clayton Hunt and Lieutenant (junior grade) Nicholas Horton, naval aviators assigned to Patrol Squadron (VP) 16, pilot a P-8A Poseidon during a mission to assist in search and rescue operations for Malaysia Airlines flight MH370 in this March 24, 2014 handout photo. 
 
 PERTH (Reuters) - An air search of the remote southern Indian Ocean resumed on Friday, seeking to confirm if hundreds of objects spotted by satellites are debris from a Malaysian jetliner presumed to have crashed almost three weeks ago with the loss of all on board. 
 
 A Chinese Ilyushin IL-76 took off from Perth before dawn, heading 2,500 km (1,550 miles) southwest into the search area where high winds and icy weather had halted flights on Thursday. 
 
 The disappearance of the Malaysia Airlines jet, which vanished from civilian radar screens less than an hour after taking off from Kuala Lumpur on a routine flight to Beijing on March 8, has gripped the world and baffled investigators. 
 
 Officials believe someone on board Flight MH370 may have shut off the plane's communications systems before flying it thousands of miles off course where it crashed into the ocean in one of the most isolated and foreboding regions on the planet. 
 
 Theories range from a hijacking to sabotage or a possible suicide by one of the pilots, but investigators have not ruled out technical problems. 
 
 The search zone centers on the latest sightings of possible wreckage that were captured by Thai and Japanese satellites in roughly the same frigid expanse of sea as earlier images reported by France, Australia and China. 
 
 "We detected floating objects, perhaps more than 300," Anond Snidvongs, the head of Thailand's space technology development agency, told Reuters. "We have never said that the pieces are part of MH370 but have so far identified them only as floating objects." 
 
 The U.S. Navy said it was sending a second P8 Poseidon maritime surveillance aircraft to help in the search for the missing Boeing 777. 
 
 "It's critical to continue searching for debris so we can reverse-forecast the wind, current and sea state since March 8th to recreate the position where MH370 possibly went into the water," said Commander Tom Moneymaker, a U.S. 7th Fleet oceanographer. 
 
 The United States has also sent a device that can be towed behind a ship to pick up faint pings from the plane's black box voice and data recorders, but time is running out. 
 
 "We've got to get this initial position right prior to deploying the Towed Pinger Locator since the MH370's black box has a limited battery life and we can't afford to lose time searching in the wrong area," Moneymaker said. 
 
 NEW IMAGES 
 
 The Australian Maritime Safety Authority, which is coordinating the effort, said it would give details later on the search after flights were halted on Thursday. 
 
 "It's the nature of search and rescue. It's a fickle beast," Flying Officer Peter Moore, the captain of an Australian AP-3C Orion, told Reuters aboard the plane after it turned around 1,000 km (600 miles) from the search zone. 
 
 "This is incredibly important to us. The reality is we have 239 people whose families want some information and closure." 
 
 The objects spotted by the Thai satellite on Monday were between 2 meters (6.5 ft) and 16 meters (52 ft) in size and were in an area around 2,700 km (1,680 miles) southwest of Perth, Snidvongs said. 
 
 The prolonged and so far fruitless search and investigation have taken a toll, with dozens of distraught relatives of 150 Chinese passengers clashing with police and accusing Malaysia of "delays and deception". 
 
 China has repeatedly voiced its frustration with the efforts of Malaysia to find the plane. China's special envoy to Malaysia said on Thursday that Beijing was doing its best to push the Southeast Asian nation to coordinate the international search effort, state news agency Xinhua said. 
 
 Chinese insurance companies have started paying compensation to the families of passengers, Xinhua reported separately. 
 
 A U.S.-based law firm has said it expects to represent families of more than half of the passengers in a lawsuit against the carrier and Boeing, alleging the plane had crashed due to mechanical failure. 
 
 (Additional reporting by Suilee Wee in Beijing, Niluksi Koswanage in Kuala Lumpur, Stanley White in Tokyo and Amy Sawitta Lefevre in Bangkok; Writing by Lincoln Feast and Alex Richardson; Editing by Dean Yates) ||||| 1 of 14. Able Seaman Boatswains Mate Rory Dow heads towards a floating object sighted from aboard a Rigid Hull Inflatable Boat deployed from the Australian Navy ship the HMAS Success as they search in the southern Indian Ocean for the missing Malaysian Airlines flight MH370 in this picture released by the Australian Defence Force April 2, 2014. 
 
 PERTH/KUALA LUMPUR (Reuters) - Malaysian police have ruled out involvement of any passengers in the disappearance of a missing jetliner, while Australian officials warned bad weather and a lack of reliable information were impeding efforts to find wreckage from the plane. 
 
 Up to 10 planes and nine ships from a half dozen countries on Wednesday scoured a stretch of the Indian Ocean roughly the size of Britain, where Malaysia Airlines Flight MH370 is believed to have crashed more than three weeks ago. 
 
 Authorities have not ruled out mechanical problems as causing the disappearance, but say all the evidence suggests the plane was deliberately diverted from its scheduled route from Kuala Lumpur to Beijing. 
 
 Malaysia's police chief said the investigation was focusing on the cabin crew and pilots, after clearing all 227 passengers of possible involvement in hijacking, sabotage or having personal or psychological problems that could have been connected to the disappearance. 
 
 "They have been cleared," national police chief Khalid Abu Bakar was quoted as saying by state news agency Bernama. 
 
 The search and rescue teams are in a race against time to locate the plane's black box recorder, which has an expected battery life of around 30 days and without which it may never be possible to find the wreckage. 
 
 Retired Air Chief Marshal Angus Houston, the head of the Australian agency coordinating the operation, said that a lack of reliable flight telemetry and punishing conditions at sea were making the operation even more challenging. 
 
 "In other words, we don't have a precise aircraft location for six hours before the aircraft went into the water somewhere," he said in an interview with the Australian Broadcasting Corporation. 
 
 "The reality is it's the most complex and challenging search and rescue operation, or search and recovery operation now, that I've ever seen." 
 
 NO TRACE 
 
 Broken clouds, sea fog and isolated thunderstorms were expected to further complicate operations, Australia's Joint Agency Coordination Center said. 
 
 The search is now focused on an inhospitable 221,000 sq km (85,000 sq miles) swathe of the southern Indian Ocean some 1,500 km (932 miles) west of the Australian city of Perth. But despite the unprecedented effort, the international team has so far failed to spot any trace of the jetliner. 
 
 "Look, it's one of the great mysteries of our time," Australian Prime Minister Tony Abbott said in an interview with local Perth radio station Radio 6iX. 
 
 "We owe it to the world, we owe it to those families, to do whatever we reasonably can do get to the bottom of this." 
 
 Malaysian Prime Minister Najib Razak was expected to arrive in Perth late on Wednesday to inspect the search and rescue operations, which are being conducted out of RAAF Base Pearce north of the city. He was expected to meet Abbott on Thursday. 
 
 Najib will arrive with Malaysia coming under fresh fire for its handling of the incident after authorities there changed their account of the plane's critical last communication. 
 
 Malaysia on Tuesday released the full transcript of communications between the Boeing 777 and local air traffic control before it dropped from civilian radar in the early hours of March 8. (for full transcript, click: r.reuters.com/kam28v) 
 
 While indicating nothing abnormal, the transcript showed the final words from the cockpit were not the casual "All right, good night" that authorities first reported, but the more standard "Good night Malaysian three seven zero." 
 
 Minutes after the final radio transmission was received the plane's communications were cut off and it turned back across Peninsular Malaysia and headed towards the Indian Ocean, according to military radar and limited satellite data. 
 
 NUCLEAR SUBMARINE 
 
 Malaysian authorities have faced heavy criticism, particularly from China, for mismanaging the search, now in its fourth fruitless week, and holding back information. Most of the 239 people on board the flight were Chinese. 
 
 Among the vessels due to join the search in the coming days is an Australian defence force ship, the Ocean Shield, that has been fitted with a sophisticated U.S. black box locator and an underwater drone. 
 
 Britain is sending HMS Tireless, a Trafalgar-class nuclear submarine with sonar capabilities, to help with the search, Malaysia's transport ministry said in a statement. 
 
 Still, Houston said the challenging search would continue based on the imperfect information with which they had to work. 
 
 "It's vitally important for the governments involved that we find this aeroplane," he said. "But I'm just pointing out that it won't be easy given the circumstances that surround this particular search and recovery operation." 
 
 (Additional reporting by Stuart Grudgings in KUALA LUMPUR; Editing by Alex Richardson) ||||| Story highlights Australian leader: "We should not underestimate the difficulty" of the search 
 
 The search for the missing Malaysia Airlines airliner has gone on for three full weeks 
 
 Authorities recently shifted the focus of the search area some 1,100 kilometers 
 
 5 aircraft spotted debris in the new area, but none is confirmed to be from Flight 370 
 
 Three weeks after Malaysia Airlines Flights 370 set off from Kuala Lumpur, search aircraft set off Saturday from Australia -- hoping to, finally, find the Boeing 777 in the southern Indian Ocean where experts now believe it ended up. 
 
 The area that search teams -- including a Chinese Ilyushin IL-76 and an Australian P-3 Orion that set off Saturday morning from Perth -- are now focusing on is 1,100 kilometers (680 miles) to the northeast from where they'd been concentrating for more than a week, and it's closer to the Australian coast. This change is thanks to a new analysis of satellite data that Australian authorities say show the commercial airliner could not have flown as far south as once thought. 
 
 Saturday's renewed search comes days after Japan and Thailand both said they'd sent new satellite images to Malaysia showing separate debris fields that could be related to the plane, which vanished with 239 people aboard. 
 
 Air Vice-Marshal Kevin Short, commander of Joint Forces New Zealand, told CNN's Erin Burnett five of the dispatched aircraft "located debris in their search area" on Friday. Some of the spottings were "hundreds of miles away" from each other, although Short said this vast expanse is "not unusual" given the ocean conditions and the time passed since the airplane's purported crash. 
 
 That includes 11 small objects spotted by one of his military's P-3 planes. CNN's Kyung Lah, who went out on a U.S. Navy P-8 search plane Friday, said the crew of that plane spotted white objects, orange rope and a blue bag. 
 
 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 
 
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 "At one point, sure, everybody on board got a little excited, but it's impossible to tell from that distance what anything is," she said. 
 
 Aircraft setting off Saturday will try to relocate those objects, take photos of them for analysis, and direct four ships in the area "to their exact location," according to Short. 
 
 But again, the world must wait -- there's no confirmation that anything spotted from the air so far has anything to do with the missing airliner, which authorities have been hunting since early March. 
 
 "We should not underestimate the difficulty of this work (in) an extraordinarily remote location," Australian Prime Minister Tony Abbott said Saturday. "... While we are throwing everything that we have at it, the task goes." 
 
 The Australian Maritime Safety Authority stressed what's been detected so far "cannot be verified or discounted as being from MH370 until they are relocated and recovered by ships," six of which are to arrive Saturday in the new search area. They could be flotsam, like one distinctive piece of fishing gear spotted in the revised zone. 
 
 This was not the first time it turned out suspected debris ended up being unrelated to the mystery plane: A Chinese aircraft reported spotting possible aircraft debris early in the search, but that sighting turned out to be nothing. 
 
 Still, Short said, "Finding debris ... gives a lot more hope." 
 
 Malaysia plane saga: Your questions answered 
 
 Better conditions 
 
 The new search zone remains vast -- roughly 123,000 square miles (319,000 square kilometers). It is still also remote -- 1,150 miles (1,850 kilometers) west of Perth. 
 
 But John Young of the Australian Maritime Safety Authority said conditions there are "likely to be better more often" than they were in the old search area, where poor weather grounded flights two days this week. 
 
 Planes will be able to spend more time in the air because the new search zone is closer to land, Young said. 
 
 U.S. flight crews involved in the search aren't frustrated or disillusioned by the sudden change in the search, Cmdr. William Marks of the Navy's U.S. 7th Fleet said. 
 
 "For the pilots and the air crews, this is what they train for," he said. "They understand it." 
 
 Marks told CNN's Anderson Cooper on Friday night that finding the debris is just part of the goal. Oceanographers could then analyze data about current, winds and more, then, to chart where they believe the bulk of the plane lies deep underwater 
 
 "Finding the debris in of itself is OK. But it's working backwards to that starting point," Marks said aboard the USS Blue Ridge. "And this area will be, hopefully, much better (than the previous search area) for that." 
 
 If and when the body of the 777 is found, the question still remains: Why did it go down? That may not be answered until investigators undertake the arduous process of retrieving the aircraft and trying to, literally, piece together what happened to it. 
 
 Wasted time? 
 
 Some analysts have raised their eyebrows at the sudden search area shift. 
 
 "Really? That much debris and we're not going to have a look at it to see what that stuff might be?" said David Gallo of the Woods Hole Oceanographic Institution, who helped lead the search for the flight recorders from Air France Flight 447, which crashed into the Atlantic Ocean in 2009. 
 
 Others lamented the amount of time, money and resources that were spent in the old search area. 
 
 "This is time that has been wasted, there's no question," said CNN aviation analyst Miles O'Brien. 
 
 Malaysian Transport Minister Hishammuddin Hussein disputed that suggestion. 
 
 "I don't think we would've done anything different from what we have done," he said. 
 
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 CNN safety analyst David Soucie said it was "a good sign" that experts had adjusted their assumptions. 
 
 "Assumptions are the key to all of this," he said. "If you assume something and you end up with a final conclusion, you have to constantly review that." 
 
 Vast, evolving search 
 
 The shifting hunt for Flight 370 has spanned oceans and continents. 
 
 It started in the South China Sea between Malaysia and Vietnam, where the plane went out of contact with air traffic controllers. 
 
 When authorities learned of radar data suggesting the plane had turned west across the Malay Peninsula after losing contact, they expanded the search into the Strait of Malacca. 
 
 When those efforts proved fruitless, the search spread north into the Andaman Sea and northern Indian Ocean. 
 
 It then ballooned dramatically after Malaysia announced March 15 that satellite data showed the plane could have flown along two huge arcs, one stretching northwest into the Asian landmass, the other southwest into the Indian Ocean. 
 
 The search area at that point reached nearly 3 million square miles. 
 
 On Monday, Malaysian Prime Minister Najib Razak said that further analysis of the data had led authorities to conclude the plane went down in the southern Indian Ocean, far from land. 
 
 Malaysian officials told the families of those on board that nobody would have survived. But many relatives have said that only the discovery of wreckage from the plane will convince them of the fate of their loved ones. 
 
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 How they're searching for debris ||||| 1 of 7. A fast response craft from Australian Defence Vessel Ocean Shield tows Able Seaman Clearance Diver Michael Arnold as he searches the ocean for debris in the search zone in the southern Indian Ocean for the missing Malaysian Airlines flight MH370 in this picture released by the Australian Defence Force April 8, 2014. 
 
 SYDNEY/PERTH, Australia (Reuters) - An Australian ship which picked up possible "pings" from the black box recorders of a missing Malaysia Airlines jetliner has been unable to detect any further signals and time is running out to narrow the massive search, officials said on Tuesday. 
 
 Angus Houston, head of the Australian agency coordinating the search for Malaysia Airlines Flight MH370, said the month-long hunt in the Indian Ocean was at a critical stage given the batteries in the black box beacons had already reached the end of their 30-day expected life. 
 
 A U.S. Navy "towed pinger locator" onboard Australia's Ocean Shield picked up two signals consistent with black box locator beacons over the weekend - the first for more than two hours and the second for about 13 minutes. 
 
 Houston said the signals represented the best lead in the search yet, but efforts to pick up the pings again had so far been unsuccessful. 
 
 "If we don't get any further transmissions, we have a reasonably large search area of the bottom of the ocean to prosecute and that will take a long, long time. It's very slow, painstaking work," said Houston. 
 
 The black boxes record cockpit data and may provide answers about what happened to the plane, which was carrying 227 passengers and 12 crew when it vanished on March 8 and flew thousands of kilometers off its Kuala Lumpur-to-Beijing route. 
 
 Authorities say evidence, including the loss of communications, suggests the plane was deliberately diverted by someone familiar with the aircraft, but have not ruled out mechanical problems. 
 
 Analysis of satellite data led investigators to conclude the Boeing 777 came down in an area some 1,680 km (1,040 miles) northwest of Perth, near where possible pings were picked up and the search is now focused. 
 
 BLUEFIN ON HOLD 
 
 An autonomous underwater vehicle (AUV) named Bluefin-21 is onboard the Ocean Shield and could be sent to look for wreckage on the sea floor, but narrowing the search zone first was critical, Houston said. 
 
 "It is a large area for a small submersible that has a very narrow field of search, and of course, it is literally crawling along the bottom of the ocean," he said. 
 
 "That's why it's so important to get another transmission and we need to continue until there's absolutely no chance the (black box) device is still transmitting." 
 
 The Bluefin will scour the ocean floor in 20-hour missions using sonar in an attempt to find the aircraft, before its findings are downloaded and analyzed on board the Ocean Shield. 
 
 If anything unusual is spotted, the sonar on board the robotic vehicle will be replaced with a camera to take a closer look. The potential search area is about 4.5 km (2.8 miles) deep, the outer reach of the Bluefin's range. 
 
 Some 133 missions have been completed so far in the multinational aerial hunt for debris in the southern Indian Ocean and would continue, officials said. 
 
 Up to 11 military planes, three civilian planes and 14 ships planned to take part in the search on Tuesday, with good weather in the search area. But so far, searchers have only turned up fishing gear and other detritus. 
 
 "Even after the black box is found, the surface search will continue because they're looking for evidence to investigate why the aircraft went down," Lieutenant Commander Adam Schantz, the officer in charge of U.S. Navy P-8 Poseidon search unit, told Reuters. 
 
 "So, we'll continue for a while trying to find anything on the surface that might give a reasoning behind the accident." 
 
 (Additional reporting by Jane Wardell in Sydney and Anuradha Raghu in Kuala Lumpur; Editing by Dean Yates and Michael Perry)
– The search for what investigators say is the "best lead" so far in the disappearance of Malaysia Airlines Flight 370 resumed in earnest at daybreak today as boats and planes searched a patch of the southern Indian Ocean for possible plane debris. So far, there has been no trace of the floating debris seen on a satellite image. Search teams ended today's mission without finding anything, CNN reports. A total of four military planes and one civilian plane joined the search today in an area Australian Prime Minister Tony Abbott describes as "about the most inaccessible spot that you can imagine on the face of the Earth," reports the BBC. China has announced that it is sending three military vessels to the area, and they may be joined by an icebreaker currently in Perth after an Antarctic mission. Australia is now planning to use human spotters—"highly skilled and trained observers" looking out the windows of low-flying planes—to search for the debris rather than radar, the New York Times reports. After two days of fruitless radar searching, an official explains that while humans are slower than radar, they might have a better chance at spotting debris. Weather conditions in the area known as the "Roaring 40s" (due to the frequent storm-force winds in latitudes between 40 and 50 degrees," explains Reuters) have hampered the search so far, and while conditions are improving, fog and low visibility are still a factor, the Guardian finds. Also troublesome: Most of the planes assisting in the search have to deal with a seven-hour round trip to the search area, meaning they only have two hours of actual search time before they have to head back to refuel, according to an Australian official quoted by NBC News. If debris is found, investigators will use computer models to try to retrace it to a crash scene that could be hundreds of miles away. "There are sophisticated models that allow you to work backwards from the current position of each piece of debris, after considering the currents and the winds and so on," an expert who helped locate the black boxes after the 2009 Air France disaster tells Reuters. "That enables you to say X marks the spot on the surface." But an Australia official cautions that the debris may have sunk since the satellite image was taken five days ago. "Something that was floating on the sea that long ago may no longer be floating," he told reporters. "It may have slipped to the bottom."