Don't call me Shirley.
I was working an adjacent sector when Stewart's plane went NORDO (quit talking). He was at an altitude where sudden decompression would certainly get your attention, but still you would have time to descend to breathable altitude.
That they did not descend indicates hypoxia slowly set in, probably from malfunctioning equipment. Investigation showed that pressurization switch was on auto, so pilot error was improbable.
The sector continued trying to contact him to no avail...often not a big deal, just a radio problem. But when he continued climbing through his assigned altitude it was suddenly a VERY big deal, fighter was borrowed from a warning area and vectored in but unable to contact him.
OK, I promise. That business with Stewart was a real shame. I always thought he was one of the classiest individuals on the tour.
So, do the oxygen masks in a pressurized cabin only drop during a sudden depressurization or will they also drop when the oxygen level in the cabin drops below a danger level? Having only ever flown non-pressurized small craft, I never really gave it much thought other than keeping my altitude under 10K.