ah, I wasn’t sure because I was reading this:

The oxygen saturation of hemoglobin determines the content of oxygen in blood. After the human body reaches around 2,100 metres (6,900 ft) above sea level, the saturation of oxyhemoglobin begins to decrease rapidly.[2] However, the human body has both short-term and long-term adaptations to altitude that allow it to partially compensate for the lack of oxygen. There is a limit to the level of adaptation; mountaineers refer to the altitudes above 8,000 metres (26,000 ft) as the death zone, where it is generally believed that no human body can acclimatize.

https://en.m.wikipedia.org/wiki/Effects_of_high_altitude_on_humans

it seemed like between 7,000 and 8,000 26,000 the air is not suitable, but I figured the pilot wasn’t likely to be taking risks like that, so there must be some explanation

edit: mixed up feet and meters