A number of theories about the causes of the Malaysia Airlines flight MH370 disappearance have circulated on the Internet – mostly launched by professional airline pilots. However, none have been embraced by any official agencies, with one constant throughout the search for the missing jet being the Malaysian authorities' belief that events early in the flight indicate “deliberate action by a person or persons on board” to divert the Boeing 777-200ER from its Kuala Lumpur-Beijing flightpath.
The aircraft was taken deliberately off course and flown away from its intended destination.
For: The aircraft made a turn off its course precisely at the point where it had been handed over from Malaysia air traffic control to Vietnam control – a move calculated to maximise the time taken before either ATC raised the alarm. There was no emergency call. Also, shortly before the airspace boundary, the aircraft’s ATC transponder was switched off to erase its contact from civilian radar screens, so the turn to the west was not witnessed. The aircraft’s technical aircraft communications addressing and reporting system (ACARS) datalink had also been disabled, although there is uncertainty as to when this took place.
Against: There is no proof that the equipment was deliberately switched off rather than accidentally deprived of power, and the loss of contact on the airspace boundary may have been coincidental.
There was a sudden depressurisation at cruising altitude. The crew were slow to don their oxygen masks and fell unconscious, and the aircraft flew on autopilot until it ran out of fuel.
For: This would explain the lack of an emergency call. The aircraft turned as if aiming for an alternate landing site – Langkawi has been repeatedly mentioned – but did not land, instead continuing across the peninsula.
Against: With no intervention from the flightcrew the aircraft would normally follow the flightpath programmed into the flight management system, but it did not do that. A decompression does not explain the loss of transponder and ACARS. Also, the record of crews worldwide dealing successfully with sudden decompression events is almost 100%.
Fire breaks out, knocking out communications and eventually leading to unconsciousness of the crew and passengers.
For: An electrical fire might explain the loss of all communications, if it were allowed to propagate for enough time without any response. It could eventually asphyxiate crew and passengers.
Against: Signs of fire (smoke and smell) since the Swissair 111 disaster in 1998 has caused crews to act particularly fast, both to communicate the emergency to ATC and to land as soon as possible. There was no communication. Also, if an electrical fire were to propagate in the avionics and communications bay area under the flightdeck it would disable the flight control systems – so the autopilot would not be able to continue to fly the aircraft for 5-7h after the crew had been disabled. Satellite systems detected continued flight for that length of time.