The Payne Stewart senario is exactly the same as the one we had in UK many years ago with a Beech King Air.
The Beech demonstrator pilot was checking a new owner pilot. Part of the drill was a de-compression at 30,000 feet.
In preparation the Oxygen was switched on ( manually by a Bowden cable on King Air) and masks were donned. the aircraft was then depressurised. Unfortunately the bowden cable had frozen ( as in iced up) and the crew slowly lost consiousness. The aircraft flew on autopilot across the Channel followed by both RAF and French Air Force aircraft until crashing in a field in France.
While flying on Photo Survey at 22,000 in a DC3 there were some very interesting situations when 02 ran low - the main thing being that people are just not aware of the problem and were unable to respond to control demands without even realising it.