wrote:

In accounts of the crash of the Cypriot airliner in Greece, all I've
read say that loss of cabin pressure could not, by itself, incapacitate
the pilot. Yet, I was once told by an ATP that at 40k feet (admittedly
this plane was at 35k) O2 supply by itself will not suffice to keep you
conscious and that the drop down masks only give a false sense of
security.

The O2 masks are intended to keep you conscious during the descent to an
altitude where they are unnecessary, as is the O2 supply for the cockpit
crew. There is not enough O2 system capacity to cruise for a long period of
time.

When minimum enroute altitudes over high terrain are coupled with O2 time
limits there are routes in the lower 48 which are not legally flyable by
commercial airliners with certain MEL restrictions, though these details are
not always clearly emphasized in information available to the pilot.


Jack

p.s. speculation about the cause of a specific accident without the benefit
of the results of the investigation is a fools' game.