Don't be too offended by me taking away some oxygen from some of your idle views. I'm talking about standard jet engines, yes they do compress air by the rotary mechanics, however at the burn rate the oxygen levels are minimal in that altitude. So nonetheless it's impressive to note that air breathing engine that need oxygen do so well at such altitudes.
common understanding, p.e. knowledge & witness to seeing people in higher altitudes show they are more robust. Tibetans have a good record of lifespan & health in comparison. Like I mentioned before they need to do more work due to geography, air etc. continually excersizing & a cleaner exchange of air. Athletes from higher altitudes also portray much better performance while in lower altitudes as they thrive in richer oxygen as their bodies are adjusted to lower levels 'thin air'.
Go to www.google.com
and type in "25000 feet in meters."
many people have climbed mount everest free of respiratory equipment which reaches close to the altitude u have indicated being almost impossible for a person.