[Banjoguy]

MH370 flew to 45,000ft - almost 2,000ft above what Boeing says is its maximum recommended height - before descending to 23,000ft.

Depressurizing the passenger compartment while the crew members used their oxygen supply would annihilate the passengers.

[RummyChick]

there are theories that Boeing knows Exactly what happened to that plane.

It seems to me that there would be something in that craft that would help them identify location - even if not known to the public.