10540
I am not saying you can fly along at 25 K without oxygen. I am saying that in pressure chamber tests not all pass out maybe 50% at that level.
I am also not saying that those who do not pass out would be wired up correctly
In the link to the test pilot article I posted you will see that he often flew to 18000/19000 feet without oxygen and on one occasion above 20K.
I think it is more than likely that this pilot passed out maybe unaware that he had NO oxygen feeding his mask at 25 K. One strange point is airways he is unlikely to have been hand flying and would have been on autopilot. The Bravo is ultra stable even off auto.
You would have thought that passing out the plane would have flown along until the fuel ran out at its programmed level?
I would also agree that at 10/12K it is a good idea to whiff some oxygen now and again to keep you sharp and especially before a night approach.
Pace