"Peter Dohm" wrote

It appears that they were lucky and the oxygen was'nt needed; but it does
remind me of some of the speculation surrunding the Paine Stewart case.
Two hypotheses around my local airport were that 1) the tank was
inadvertantly filled with nitrogen or 2) that someone misread the labeling
on the regulator on/off handle--which is counterintuitively labeled with
"on" or "off" and arrows pointing which direction to turn the knob for the
desired result. I don't recall whether the case was ever fully resolved;
but a lot of pilots found a couple of areas worthy of their maximum
vigilance!

Learjets don't use bottled oxygen; they have pressurized air from the
engines.

The fact that it was level and on autopilot would suggest that they did not
have a problem with the pressurization system that was noticed, that would
have caused them to try to go onto the bottled oxygen.
--
Jim in NC