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

[–] azertyfun@sh.itjust.works 3 points 5 days ago (1 children)

You're mixing up feet and meters. The death zone is at 8 km, i.e. 26k ft.

2100m is barely mountaineering, you can bring grandma and the newborn hiking there and at most you'll notice a mild shortness of breath.

In fact normal cabin pressure at cruising altitude is equivalent to 7000 ft. Besides a lot of ear popping most people don't even notice it, though mild altitude sickness (i.e. a small headache) is possible, but ultimately harmless.

[–] dandelion@lemmy.blahaj.zone 2 points 5 days ago

ah, that explains my confusion - thank you for clearing that up!

[–] Dempf@lemmy.zip 2 points 5 days ago

7-8k is fine. There are many towns in the U.S. at or above that elevation.

[–] Cocodapuf@lemmy.world 2 points 5 days ago* (last edited 5 days ago)

it seemed like between 7,000 and 8,000 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

Yeah, I mean the atmospheric pressure at altitude varies, it's definitely not black and white. And it's true, pressure does start to really drop off around 7000ft, but it's just starting to drop significantly at that point, that just makes 7k a good ceiling.

So yeah, this all seems pretty much consistent.