There was a post on reddit/r/multicopter a while ago of prop thrust at different air pressures with the same current. It's pretty much exactly what you're askin

There was a post on reddit/r/multicopter a while ago of prop thrust at different air pressures with the same current. It's pretty much exactly what you're asking for. https://i.imgur.com/Z5toIVm.jpg https://i.imgur.com/Z5toIVm.jpg Assuming air pressure at 10000 ft is ~69kpa, and sea level is ~100kpa, there really doesnt appear to be much of a difference, except for medium-sized props, which had very interesting thrust outputs- gaining efficiency at low rpm and loosing a lot at high rpm. Anyway, point being is a 250 class quad could pretty easily fly at 10000 feet. Not particularly well, but considering 1:4 (or even 1:8) thrust ratios arent uncommon with 250 class quads they could still pull it off. Now, idk about bigger quads like the phantom/iris, their props have quite different geometries which probably act quite differently.