Piracy and pilot suicide are among the scenarios under study as investigators grow increasingly certain the missing Malaysian Airlines jet changed course and headed west after its last radio contact with air traffic controllers.
The latest evidence suggests the plane didn't experience a catastrophic incident over the South China Sea as was initially suspected. Some experts theorize that one of the pilots, or someone else with flying experience, hijacked the plane or committed suicide by plunging the jet into the sea.
A U.S. official said Friday in Washington that investigators are examining the possibility of "human intervention" in the plane's disappearance, adding it may have been "an act of piracy." The official, who wasn't authorized to talk to the media and spoke on condition of anonymity, said it also was possible the plane may have landed somewhere.
While other theories are still being examined, the official said key evidence suggesting human intervention is that contact with the Boeing 777's transponder stopped about a dozen minutes before a messaging system on the jet quit. Such a gap would be unlikely in the case of an in-flight catastrophe.
A Malaysian official, who also declined to be identified because he is not authorized to brief the media, said only a skilled aviator could navigate the plane the way it was flown after its last confirmed location over the South China Sea. The official said it had been established with a "more than 50 per cent" degree of certainty that military radar had picked up the missing plane after it dropped off civilian radar.
Malaysia's acting transport minister, Hishammuddin Hussein, said the country had yet to determine what happened to the plane after it ceased communicating with ground control around 40 minutes into the flight to Beijing on March 8 with 239 people aboard.
He said investigators were still trying to establish with certainty that military radar records of a blip moving west across the Malay Peninsula into the Strait of Malacca showed Flight MH370.
"I will be the most happiest person if we can actually confirm that it is the MH370, then we can move all (search) assets from the South China Sea to the Strait of Malacca," he told reporters. Until then, he said, the international search effort would continue expanding east and west from the plane's last confirmed location.
On Thursday, a U.S. official said the plane remained airborne after losing contact with air traffic control, sending a signal to establish contact with a satellite.
Boeing offers a satellite service that can receive a stream of data on how an aircraft is functioning in flight and relay the information to the plane's home base. Malaysia Airlines didn't subscribe to that service, but the plane still had the capability to connect with the satellite and was automatically sending signals, or pings, said the U.S. official, who spoke on condition of anonymity because he wasn't authorized to discuss the situation by name.
Scores of aircraft and ships from 12 countries are involved in the search, which reaches into the eastern stretches of the South China Sea and on the western side of the Malay Peninsula, northwest into the Andaman Sea and the Indian Ocean.