Originally Posted by
Sailvi767
Most modern airliners are not altitude limited by performance. The Max allowed altitudes are based on the time it takes to reach 10,000 feet in a decompression. Many pilots also assume the Max altitude is simply that number. Depending on the aircraft type it may be a pressure altitude so requesting FL 410 might be above the max allowed altitude.
A large part of its limit is a function of engine thrust to maintain speed. The 787 runs out of thrust before it does “wing” in a high level climb compared to older types