The disappearance of a Malaysian plane is an "unprecedented aviation mystery", a senior official says, with a massive air and sea search now in its third day failing to find any confirmed trace of the plane or 239 people aboard.
The Malaysian Airlines Boeing 777-200 disappeared from radar screens in the early hours of Saturday, about an hour into its flight from Kuala Lumpur, after climbing to a cruising altitude of 35,000 feet.
The head of Malaysia's Civil Aviation Authority, Azharuddin Abdul Rahman, said a hijacking could not be ruled out as investigators explore all theories for the loss of flight MH370 en route to Beijing, Reuters reports. "As far as we are concerned, we have to find the aircraft, we have to find a piece of the aircraft if possible."
A Vietnamese navy plane reported seeing what could have been a piece of the aircraft as darkness fell across the Gulf of Thailand and South China Sea on Sunday, but ships and aircraft returning in daylight have so far found nothing.
No distress signal was sent from the plane, which experts said suggested a sudden catastrophic failure or explosion, but Malaysia's air force chief said radar tracking showed it may have turned back from its scheduled route before it disappeared.
A senior source involved in preliminary investigations in Malaysia said the failure to quickly find any debris indicated that the plane may have broken up mid-flight at about 35,000 feet which could disperse wreckage over a very wide area. Asked about the possibility of an explosion, such as a bomb, the source said there was no evidence yet of foul play and the plane could have broken up due to mechanical causes.
About two-thirds of the 227 passengers and 12 crew now presumed to have died were Chinese. The airline said other nationalities included 38 Malaysians, seven Indonesians, six Australians, five Indians, four French and three Americans.
On the flight also were two New Zealanders - Ximin Wang, 50, from Auckland and described in the electoral roll as a student, and 38-year-old Paul Weeks.
Mr Weeks was heading to Mongolia to start a job as a mining contractor. He had moved to the Australian city of Perth from Christchurch two years ago and last contacted his family from the airport lounge in the Malaysian capital.
His wife, Danica Weeks, said Malaysia Airlines has offered to pay for flights for two family members to Kuala Lumpur. However, she dismissed the idea because of her young children, saying it looked like chaos.
A New Zealand Air Force Orion on Monday joined the search.
Two used stolen passports, five didn't board
As dozens of ships and aircraft from seven countries scour the seas around Malaysia and south of Vietnam, questions mounted over possible security lapses and whether a bomb or hijacking could have brought down the Boeing airliner.
Interpol confirmed that two passengers on the flight used stolen Austrian and Italian passports, raising suspicions of foul play. Both passengers bought their tickets for the flight from Kuala Lumpur to Beijing at the same time.
The passenger manifest issued by Malaysia Airlines included the names of Austrian Christian Kozel and Italian Luigi Maraldi - who were not on the plane and whose passports had been stolen in Thailand during the past two years.
A spokesperson for Interpol said a check of all documents used to board the plane had revealed more suspect passports that were being further investigated.
Steve Vickers, a Hong Kong analyst who works for a security consulting company, told Radio New Zealand's Checkpoint programme on Monday there are weak spots for people using fake passports and the practice is far too common.
Five passengers who failed to board the flight are also being investigated by intelligence agencies. Malaysian Airlines says their baggage was removed.
Malaysian Transport Minister Hishammadin Hussein said the entire passenger list of the flight is being investigated by the intelligence service and counter-terrorism agents.
Malaysia's state news agency quoted Home Minister Ahmad Zahid Hamidi as saying the two passengers using the stolen European passports were of Asian appearance, and criticised the border officials who let them through.
Boeing said it was monitoring the situation. The Boeing 777 has one of the best safety records of any commercial aircraft in service. Its only previous fatal crash came on 6 July last year when Asiana Airlines flight 214 struck a seawall on landing in San Francisco, killing three people.