Malaysian authorities have been accused of holding back information about why a plane carrying 239 people vanished in Southeast Asia.
Aviation experts told Sky News pilot suicide is a possible explanation, although Malaysia Airlines chiefs say there is "no reason to believe" crew had anything to do with the Boeing 777-200's disappearance.
Five days on from its disappearance, there is still no sign of flight MH370, despite a massive search and hundreds of planes flying over the area.
:: Sky News will be showing a 12-minute special report on the story so far of the missing flight at 6.30pm.
As the mystery deepened, Australian aviation consultant Neil Hansford accused the Malaysian government of not telling the full story of what happened.
He told Sky News: "I'm finding in any interviews I'm doing with Malaysians, there is a fair bit of spin, there's a fair bit of denial of the boarding procedures and the manifest checking with the stolen passport list, and inconsistencies all the time.
"I think you're now finding the Malaysian authorities have got a lot to answer for."
He said when he heard the news on Saturday, he suspected it was one of three things.
The first is that the aircraft was hit by a military aircraft or military ordnance and had a catastrophic failure.
The second is that there was a bomb on board.
"Nothing that I'm hearing is giving me any warmth about the two passengers with the stolen passports," he said.
"If they were heading for Germany, why would they be on a Malaysian aircraft going to China? It just doesn't make sense."
Mr Hansford's third scenario - and the most likely in his view - is pilot suicide.
"Now I don't know which pilot was flying, whether it was the captain or the first officer, but all of this starts to indicate why we cannot find any wreckage, and why the aircraft didn't make scheduled contact with control."
John Hansman, professor of aeronautics at the Massachusetts Institute of Technology, also believes pilot suicide is a possibility.
The plane vanished around an hour into its flight from Kuala Lumpur to Beijing.
According to military radar, the plane turned back from its scheduled route, but this has now been denied by the Malaysian air force.
Mr Hansman said: "If the military radar is correct, and we don't know for sure if they were tracking the right target ... it would be consistent with an intentional act by someone in the cockpit to turn off both the transponder and turn the aircraft on to a new course."
Another theory is there was pressurisation failure and the pilots put on oxygen masks and turned back to Kuala Lumpur before passing out.
But both experts believe this is unlikely.
Mr Hansford said: "If it had turned back, the Malaysian air force would have gone into the skies. The aircraft was allegedly not emitting any transponder signals, so it would have been a foreign aircraft over Malaysia."
"There's no technical or mechanical failure or any other reason I can come up with that would cause an aircraft to both lose its transponder, still fly and change course," added Mr Hansman.
"So it doesn't appear to be a crew incapacitation or anything like that."
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