A November 2013 FAA Airworthiness Directive for the 777
http://www.gpo.gov/fdsys/pkg/FR-2013...2..." onclick="window.open(this.href);return false;.
SUMMARY: 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.
Summary: Its plausible that a fuselage section near the SATCOM antenna adapter failed, disabling satellite based - GPS, ACARS, and ADS-B/C - communications, and leading to a slow decompression that left all occupants unconscious. 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 golfball-sized hole) would have gradually impaired and confused the pilots before cabin altitude (pressure) warnings sounded.
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, its possible the pilots did not realize to put on oxygen masks until it was too late. (See Helios 522)
Also explains why another Pilot thirty minutes ahead heard mumbling from MH370 pilots.
(VHF comms would be unaffected by SATCOM equipment failure.)
With incapacitated pilots, the 777 could continue to fly on Autopilot - programmed to maintain cruise altitude and follow the programmed route. Using the Inertial Reference System (gyroscope based), the plane could navigate without needing GPS.
Other thoughts:
The plane was equipped with cellular communication hardware, supplied by AeroMobile, to provide GSM services via satellite. However this is an aftermarket product; its not connected through SATCOM (as far as I know).
This explains why 19 families signed a statement alleging they were able to call the MH370 passengers and get their phones to ring, but with no response.
When Malaysian Airlines tried to call the phone numbers a day later, the phones did not ring. By this time, fuel would have been exhausted.
Note: 777 Passenger Oxygen masks do not deploy until cabin altitude reaches 13,500. Passengers were likely already unconscious by then, if it was a slow decompression. Also remember that this flight was a red-eye, most passengers would be trying to sleep, masking alarming effects of oxygen deprivation. No confirmed debris has been found anywhere near the search area, consistent with the plane having flown for hours after it lost radar contact.
Conclusion:
This was likely not an explosive decompression or inflight disintegration. This was likely a slow decompression that gradually deprived all crew/passengers of oxygen, leaving the autopilot to continue along the route autonomously.