Crew O2 Bottle goes bang, takes out xpndr, comms and leaves a large hole in the fuselage.
Crew dons masks, starts the process of running through checklists, calling ATC etc.
PF could have easily selected a southerly HDG mode during these initial moments. Nearest runway?
I have experienced hypoxia in a pressure chamber and can understand how it could have caused unexpected and illogical handling as the mental processing power of the crew degraded toward unconsciousness and death.
I am not an investigator, but it certainly seems a reasonable possibility among others.
Well it must have seemed plausible to the Captain of MH370 who had prepared himself for dealing with just such a hypoxia induced change of route by rehearsing it on his home simulator. Twice.
