Malaysia Airliner Communications Shut Down Separately: US Officials Say

[Xithras]

16. Doesn't eliminate the fire possibility.

Read an interesting theory on that one earlier. It went something like this:

1. Electrical fire started in the cockpit, taking out primary radio communications.
2. Pilot turned the aircraft around in an attempt to go back for help, before being killed, incapacitated, or chased out of the cockpit.
3. Fire burned through enough of the cockpit to shut down other electrical systems, including cabin pressurization controls.
4. Oxygen levels dropped, knocking out the passengers and dropping the fire to a smolder.
5. The plane flew on under autopilot until the fire either spread far enough to take it out of the sky, or the jet ran out of fuel.

I don't know enough about the 777's electrical systems to know how plausible this is, but at a 10,000 foot level it sounds as plausible as any other theory.