commercial aircraft have a service ceiling around 60,000 ft so they'll never go too high.
anyway pilot/autopilot makes adjustments to stay within their 1000' of assigned airspace upto 18000'ft agl and flight levels 18,0 asl.
also flat earthers are not worth arguing against. not sure if troll or brainwashed.
The U2 spy plane could fly at 80,000 feet and did not have autopilot to make adjustments. Rather than just saying I am a troll or brainwashed---just look at the data for yourself.
I said commercial.
Right---a U2 spy plane goes even higher. In either case, a plane does not need to make constant adjustments downward to correct for the Earth's curvature.