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Well stated post by that guy.

Unlike that poster I am a pilot, a retired fighter pilot, as well as a USAF trained Life Support Officer that was trained at Kelly AFB and Brooks.

Mechanical failure if back-up Oxygen systems are there in case of emergency. The issue is one of mechanical reliability and an aircrew’s ability to react in a timely manner.

Mechanical reliability of systems rarely ever deployed is problematic and involved regular maintenance checks, which by the way, do add a human error element in the reliability of the system. Also, we are talking a foreign maintenance program. Foreign maintainers are notorious for their lack of reliability and safety practices. Indeed, Cypress is ranked very low for maintenance practices and safety.

As far as the aircrew reacting, if the warning are not present they do have a cabin altimeter they can reference, but here is the thing: A reliance on the back-up system and warning systems does lead to complacency and complacency will affect their discipline to actually read the gauge. Of course, in a climb you reference the gauge to make sure cabin pressurization is working, and that is usually done when climbing through 10,000 feet. If it looks good at that time you rely more on the bells and whistles rather than the gauge.

Now, if the pilots succumbed to Oxygen deprivation (hypoxia) due to a slow leak, the discovery of their hypoxia symptoms may be slow in coming. . .too slow to discover. They would slowly, and without really noticing, pass out.

With rapid decompression the effects are felt (and usually heard) and see and reacted too. TUC, (time of useful consciousness) varies with altitude. At FL35 I think it is around 20 secs to react, with less time if higher and more time if lower.

So, if the aircraft experienced rapid decompression the aircrew would have known and reacted quickly, and if the cockpit oxygen back-up system was still functioning, they would have survived.

If the hypoxia were due to a slow leak then they would have passed out not knowing what was happening. Of course, as the aircraft descended to a lower altitude the aircrew would recover, but they recovery is not like you see in movies. There is not magic moment of awakening. . it is a wakening where the aircrew are confused and unsure and groggy. If there is enough time then they may recover fully to save the jet, if not, they die.

Right now we simply don't know what happened. We have no facts, no flight data recorder, and we certainly have no survivor from the cockpit to tell us what happened.

The supposed text message is interesting in that the guy that sent the text was likely metabolically more fit than others and that might explain the message.

Anything else right now is guesswork only, and I as, irresponsible.

Now, for real, I'm outta here.

Of course, as the aircraft descended to a lower altitude the aircrew would recover

If they were still alive. Can you say whether the ambient air pressure at 35,000 feet enough to substain life for an hour, or is it more likely that one will die, without a working air mask? Obviously, the answer could depend on the cardiovascular health of the victim. I can imagine that a Himalayan Sherpa would last longer than a diabetic old man.

They would slowly, and without really noticing, pass out.

That much I can vouch for. In my brief stint in pilot training school (before I decided that flying over Hanoi was too risky, and took a desk job) I did a training run in a high altitude chamber, removing my mask as part of an exercise to learn what it's like to loose air at high altitude. If I am ever sentenced to the death penalty, I want to go out that way. I happily faded away without the slightest distress. If the trainer had not put my mask back on, I would have been quite dead. It's way too easy.

In any case, my favorite speculation of the moment is that the text messaging cousin in the cabin had a working mask, but the pilot didn't, probably due to normal equipment failure and inadequate maintenance. Whether it was equipment failure or terrorists that caused the initial depressurization - that I have no bias on, yet.