An airplane cabin, at altitude, is only pressurized to an altitude of 8,000 feet. Being a pilot, I experience that altitude all the time and I feel comfortable with it.
It’s a whole different world trying to trail run at that altitude, however, particularly when the top of the hike is at almost 9,000 feet. That’s what happens when you go trail running or hiking in the Spring Mountains National Recreation Area near Las Vegas, NV.