KUALA LUMPUR/HO CHI MINH CITY A Malaysia Airlines flight carrying 227 passengers and 12 crew was presumed to have crashed off the Vietnamese coast on Saturday, and European officials said two people on board were using false identities. 
 
 There were no reports of bad weather and no sign of why the Boeing 777-200ER would have vanished from radar screens about an hour after it took off from Kuala Lumpur for Beijing. 
 
 "We are not ruling out any possibilities," Malaysia Airlines CEO Ahmad Jauhari Yahya told a news conference. 
 
 By the early hours of Sunday, there were no confirmed signs of the plane or any wreckage, well over 24 hours after it went missing. Operations will continue through the night, officials said. 
 
 There were no indications of sabotage nor claims of a terrorist attack. But the passenger manifest issued by the airline included the names of two Europeans - Austrian Christian Kozel and Italian Luigi Maraldi - who, according to their foreign ministries, were not in fact on the plane. 
 
 A foreign ministry spokesman in Vienna said: "Our embassy got the information that there was an Austrian on board. That was the passenger list from Malaysia Airlines. Our system came back with a note that this is a stolen passport." 
 
 Austrian police had found the man safe at home. The passport was stolen two years ago while he was travelling in Thailand, the spokesman said. 
 
 The foreign ministry in Rome said no Italian was on the plane either, despite the inclusion of Maraldi's name on the list. His mother, Renata Lucchi, told Reuters his passport was lost, presumed stolen, in Thailand in 2013. 
 
 U.S. and European security officials said that there was no proof of any terrorist link and there could be other explanations for the use of stolen passports. 
 
 NO MAYDAY 
 
 The 11-year-old Boeing, powered by Rolls-Royce Trent engines, took off at 12:40 a.m. (1640 GMT Friday) from Kuala Lumpur International Airport and was apparently flying in good weather conditions when it went missing without a distress call. 
 
 Flight MH370 last had contact with air traffic controllers 120 nautical miles off the east coast of the Malaysian town of Kota Bharu. Flight tracking website flightaware.com showed it flew northeast after takeoff, climbed to 35,000 feet and was still climbing when it vanished from tracking records. 
 
 A crash, if confirmed, would likely mark the 777's second fatal incident in less than a year, and its deadliest since entering service 19 years ago. An Asiana Airlines Boeing 777-200ER crash-landed in San Francisco in July 2013, killing three passengers and injuring more than 180. 
 
 Boeing said it was monitoring the situation but had no further comment. 
 
 Paul Hayes, director of safety at Flightglobal Ascend aviation consultancy, said the flight would normally have been at a routine stage, having reached initial cruise altitude. 
 
 "Such a sudden disappearance would suggest either that something is happening so quickly that there is no opportunity to put out a mayday, in which case a deliberate act is one possibility to consider, or that the crew is busy coping with what whatever has taken place," he told Reuters. 
 
 He said it was too early to speculate on the causes. 
 
 A large number of planes and ships from several countries were scouring the area where the plane last made contact, about halfway between Malaysia and the southern tip of Vietnam. 
 
 "The search and rescue operations will continue as long as necessary," Malaysian Prime Minister Najib Razak told reporters. He said his country had deployed 15 air force aircraft, six navy ships and three coast guard vessels. 
 
 Search and rescue vessels from the Malaysian maritime enforcement agency reached the area where the plane last made contact but saw no sign of wreckage, the Malaysian Maritime Enforcement Agency said. 
 
 Vietnam said its rescue planes had spotted two large oil slicks, about 15 km (9 miles) long, and a column of smoke off its coastline, but it was not clear if they were connected to the missing plane. 
 
 China and the Philippines also sent ships to the region to help, while the United States, the Philippines and Singapore dispatched military planes. China also put other ships and aircraft on standby. 
 
 NO DISTRESS CALL 
 
 The disappearance of the plane is a chilling echo of an Air France flight that crashed into the South Atlantic on June 1, 2009, killing all 228 people on board. It vanished for hours and wreckage was found only two days later. 
 
 John Goglia, a former board member of the National Transportation Safety Board, the U.S. agency that investigates plane crashes, said the lack of a distress call suggested that the plane either experienced an explosive decompression or was destroyed by an explosive device. 
 
 "It had to be quick because there was no communication," Goglia said. 
 
 He said the false identities of the two passengers strongly suggested the possibility of a bomb. 
 
 "That's a big red flag," he said. 
 
 If there were passengers on board with stolen passports, it was not clear how they passed through security checks. 
 
 International police body Interpol maintains a database of more than 39 million travel documents reported lost or stolen by 166 countries, and says on its website that this enables police, immigration or border control officers to check the validity of a suspect document within seconds. No comment was immediately available from the organization. 
 
 Italian police said the passport of Luigi Maraldi was reported stolen on August 1, 2013 and was inserted in the Interpol database 
 
 RELATIVES ANGRY 
 
 Chinese Foreign Minister Wang Yi told reporters in Beijing that China was "extremely worried" about the fate of the plane and those on board. Chinese passengers' relatives angrily accused the airline of keeping them in the dark, while state media criticized the carrier's response as poor. 
 
 "There's no one from the company here, we can't find a single person. They've just shut us in this room and told us to wait," said one middle-aged man at a hotel near Beijing airport where the relatives were taken. 
 
 "We want someone to show their face. They haven't even given us the passenger list," he said. 
 
 Another relative, trying to evade a throng of reporters, muttered: "They're treating us worse than dogs." 
 
 The airline said people of 14 nationalities were among the 227 passengers, including at least 152 Chinese, 38 Malaysians, seven Indonesians, six Australians, five Indians, four French and three Americans. 
 
 In Kuala Lumpur, Malaysia Airlines told passengers' next of kin to come to the international airport with their passports to prepare to fly to the crash site, once it was identified. 
 
 About 20-30 families were being kept in a holding room at the airport, where they were being guarded by security officials and kept away from reporters. 
 
 Malaysia Airlines has one of the best safety records among full-service Asia-Pacific carriers. 
 
 It identified the pilot of MH370 as Captain Zaharie Ahmad Shah, a 53-year-old Malaysian who joined the carrier in 1981 and has 18,365 hours of flight experience. 
 
 (Additional reporting by Stuart Grudgings and Niki Koswanage in KUALA LUMPUR, Ben Blanchard, Jonathan Standing and Natalie Thomas in BEIJING, Martin Petty in HANOI, Alwyn Scott in NEW YORK, Morag MacKinnon in PERTH, Michael Shields in VIENNA, and Naomi O'Leary in ROME, Tim Hepher in PARIS and Mark Hosenball in WASHINGTON; Writing by Raju Gopalakrishnan and Mark Trevelyan; Editing by Sonya Hepinstall) ||||| Using a system that looks for flashes around the world, the Pentagon reviewed preliminary surveillance data from the area where the plane disappeared and saw no evidence of an explosion, said an American government official who spoke on the condition of anonymity because the subject matter is classified. A team of aviation experts led by the National Transportation Safety Board was on its way to the area. 
 
 If all aboard were killed, it would be the deadliest commercial airline accident since Nov. 12, 2001, when an American Airlines Airbus crashed just after takeoff from Kennedy Airport en route to the Dominican Republic. 
 
 A senior American intelligence official said law enforcement and intelligence agencies were investigating the issue of the stolen passports. American authorities were scrutinizing the flight manifest closely, the official said, noting that forged travel documents are also used routinely by smugglers and illegal immigrants. 
 
 “At this time, we have not identified this as an act of terrorism,” said the official, who spoke on the condition of anonymity Saturday because of the continuing inquiry. “While the stolen passports are interesting, they don’t necessarily say to us that this was a terrorism act.” 
 
 A European counterterrorism official said the Italian man whose passport was stolen, Luigi Maraldi, 37, called his parents from Thailand, where he is vacationing, after discovering that someone by the same name was listed on the passenger manifest. The official, who spoke on the condition of anonymity, said Mr. Maraldi reported the theft last August to the Italian police. The official said the passport of the Austrian man, Christian Kozel, 30, who is currently in Austria, was stolen about two years ago. 
 
 Image Oil slicks on the surface of the Gulf of Thailand may have been from a crash. Credit Agence France-Presse — Getty Images 
 
 The European official said that he was surprised it had been possible to check in with stolen passports at the Kuala Lumpur airport and that an alert should have popped up on the airline agent’s computer. 
 
 Operating as Flight MH370, the plane left Kuala Lumpur just after midnight, headed for Beijing. Air traffic control in Subang, a suburb of Kuala Lumpur, lost contact with the plane around 1:30 a.m. on Saturday, Malaysia’s civil aviation department said. 
 
 China Central Television said that according to Chinese air traffic control officials, the aircraft never entered Chinese airspace. 
 
 At a news conference in Beijing after the arrival of a team of employees to assist families of the passengers in China, an official of Malaysia Airlines said the missing plane had no history of malfunctions. “It was last inspected 10 days ago, well before scheduled service,” said the executive, Ignatius Ong. “It was all in top condition.” 
 
 When pressed about possible security lapses, he repeated several times that the airline had no confirmation from the Malaysian authorities that passengers had boarded with stolen passports. 
 
 Image Ahmad Jauhari Yahya, the chief executive of Malaysia Airlines, addressed the media as the search for the plane continued. Credit Samsul Said/Reuters 
 
 Malaysia, the United States and Vietnam dispatched ships and aircraft to the mouth of the Gulf of Thailand on Saturday to join an intensive search, and the state-run Xinhua news agency said China was sending a Coast Guard vessel and two naval ships. The Chinese Ministry of Transport said a team of scuba divers who specialize in emergency rescues and recovery had been assembled on Hainan, the southern island-province, to prepare to go on Sunday to the area where the airliner may have gone down. 
 
 Lai Xuan Thanh, the director of the Civil Aviation Administration of Vietnam, said on Saturday that a Vietnamese Navy AN26 aircraft had discovered oil on the surface of the water toward the Vietnam side of the mouth of the Gulf of Thailand, east of the Malaysian Peninsula. The oil is suspected to have come from the missing plane, he added. 
 
 But on Sunday, Malaysia’s defense minister, Hishammuddin Hussein, added a confusing twist, saying the plane might have gone down west of the Malaysian peninsula. “We are looking at the possibility of an aircraft air turnback,” he said without elaborating whether the plane might have changed course for mechanical reasons or a hijacking, or why the authorities suspected the plane might have reversed course. 
 
 Malaysia Airlines said the plane had 227 passengers aboard, including two toddlers, and an all-Malaysian crew of 12. According to the manifest, the passengers included 154 citizens of China or Taiwan, 38 Malaysians, seven Indonesians, six Australians, five Indians, four French and three Americans, as well as two citizens each from Canada, New Zealand and Ukraine and one each from Austria, Italy, the Netherlands and Russia — although the true nationalities of the passengers carrying the Austrian and Italian passports are still unknown. 
 
 The family of one of the Americans aboard the flight, Philip Wood, an IBM employee in Kuala Lumpur, said they had little information beyond what had been reported in the news media. 
 
 Image A distraught couple at the Beijing Capital International Airport wait for news about the missing Malaysia Airlines flight. Credit Kim Kyung-Hoon/Reuters 
 
 “We’re relying on our Lord,” Mr. Wood’s father, Aubrey, said from his home in Keller, Tex. “He’s the one who carries the load.” 
 
 The tickets to the holders of the stolen Austrian and Italian passports were sold by China Southern Airlines, which has a code share agreement with Malaysia Airlines, according to China Southern’s account on Sina Weibo, the Chinese microblog platform. China Southern said it sold five other tickets to the flight: to the Dutch passenger, the Ukrainians, and one Malaysian and one Chinese passenger. 
 
 Arnold Barnett, a longtime Massachusetts Institute of Technology specialist in aviation safety statistics, said that before the disappearance of the plane, Malaysia Airlines had suffered two fatal crashes, in 1977 and 1995. Based on his estimate that Malaysia Airlines operates roughly 120,000 flights a year, he calculated that the airline’s safety record was consistent with that of airlines in other fairly prosperous, middle-income countries, but had not yet reached the better safety record of airlines based in the world’s richest countries. 
 
 Malaysia has not been targeted in terrorist attacks in recent decades, although the 1977 crash was attributed to a hijacking. But some of the planning for the Sept. 11 attacks in the United States was done in Malaysia, which has a relatively lax visa policy. The country is a major trading nation and a natural meeting place for a variety of groups involved in illicit activities. 
 
 The plane’s disappearance came at the end of the annual National People’s Congress in Beijing, and took place at a time of rising concern in China about terrorism. Mr. Ahmad Jauhari of Malaysia Airlines said early on in a statement that there was speculation that the plane had landed safely somewhere along the route to Beijing. But in a telephone interview before reporting the sighting of the oil in the ocean, Mr. Lai expressed concern about the aircraft’s fate. 
 
 “The possibility of an accident is high,” he said.
– It's well past midnight in Malaysia, where the search for Flight MH370 is on hold until daylight, but developments are continuing to trickle out—though the updates are far from clarifying ones. The Financial Times follows up a report on the two men—one using an Italian passport, one Austrian—who boarded the plane using stolen passports. A Thai travel agent told the paper that the tickets were booked through an Iranian middleman who goes by "Mr. Ali." She says she has booked tickets for him for the past three years, and there is no indication that "Ali" was aware the passports were stolen; the agent says Ali often booked travel for his contacts. He had asked her to arrange for the tickets March 1, and the men were originally on different airlines: Qatar and Ethiad (they had different end destinations). But the reserved tickets ultimately expired, with Ali reaching out again on Thursday; the men were then booked on Malaysia Airlines. Now Malaysian authorities have given the US images of the two men, a US official tells CNN. Meanwhile: The Wall Street Journal reports that Malaysian authorities are looking into five people who checked into the flight but didn't board—a not uncommon occurrence. Their luggage was removed from the flight before it departed. The search area is now bigger, and includes a portion of the strait of Malacca and more of the South China Sea, per the Guardian. The director general of Malaysia's Department of Civil Aviation says that's an area with a 100-nautical-mile radius, double the previous size. China is lending space satellites to the search.