Larry Dighera wrote:

I'm sure you are correct about the difference between individual
tolerance to hypoxia. I recall reading that General Yeager was able
to withstand operating at 20,000' without oxygen.

Nearly all of the pilots in the Great War could. Only some of the German aircraft
had oxygen systems, and I've not heard of any Allied aircraft that did. Ceiling
on the S.P.A.D. was 6,000 meters, according to Nordhoff and Hall.

George Patterson
Battle, n; A method of untying with the teeth a political knot that would
not yield to the tongue.