Missing Malaysian airlines flight and terror strike probe
Malaysia Airlines planes sit on the tarmac at the Kuala Lumpur International AirportReuters

A new theory as to what happened to missing Malaysia Airlines flight MH370 has been posted online, suggesting that a slow decompression of the cabin left both passengers and pilots unconscious.

Posted anonymously on tumblr, the theory cites a US Federal Aviation Administration (FAA) Airworthiness Directive from November 2013. Whoever is behind the theory claims to have emailed it to the National Transport Safety Board, in the hope that they "will consider if it's worthy of forwarding onto investigators".

The directive is a worldwide warning to be on the lookout for cracks in the fuselage of Boeing 777s underneath the satellite antenna.

It reads: "We propose to adopt a new Airworthiness Directive (AD) for certain The Boeing Company Model 777 airplanes. This proposed AD was prompted by a report of cracking in the fuselage skin underneath the satellite communication [SATCOM] antenna adapter.

"This proposed AD would require repetitive inspections of the visible fuselage skin and doubler if installed, for cracking, corrosion, and any indication of contact of a certain fastener to a bonding jumper, and repair if necessary.

"We are proposing this AD to detect and correct cracking and corrosion in the fuselage skin, which could lead to rapid decompression and loss of structural integrity of the airplane."

The FAA's basis for the proposal was an inspection of a 14-year-old Boeing 777 owned by an unnamed airline, which uncovered a 16-inch crack.

The theory's author goes on to suggest that a small, golf ball-sized hole in the fuselage on that part of the plane could have caused communications to fail and resulted in all 239 passengers and crew onboard the plane slowly drifting into unconsciousness.

"If such decompression left the aircraft intact, then the autopilot would have flown the planned route or otherwise maintained its heading/altitude until fuel exhaustion. A slow decompression [e.g. from a golf ball-sized hole] would have gradually impaired and confused the pilots before cabin altitude [pressure] warnings sounded."

The writer proposes the following chain of events:

  • Likely fuselage failure near SATCOM antenna adapter, disabling some or all of GPS, ACARS, ADS-B, and ADS-C antennas and systems.
  • Thus, only primary radars would detect the plane. Primary radar range is usually less than 100nm, and is generally ineffective at high altitudes.

If the decompression was slow enough, the writer believes that the pilots would not have realised it and would have been unable to put on their oxygen masks in time. It is also noted that the flight was a "red-eye" meaning many passengers would have been trying to sleep, therefore making the affects of oxygen deprivation less obvious.

The theory may also explain why "another pilot thirty minutes ahead heard "mumbling" from MH370 pilots."

In summary the theory recommends that flight investigators "obtain data logs from primary radars throughout mainland China that would have been along the planned route" and "obtain all passengers' cell phone log and location data" in an attempt to find the last successful connection.

19 families of those on board signed a statement alleging that they were able to call the passengers but were unable to get through, despite the phones ringing.