system
Given the following post, respond as if you're commenting on Reddit:
human
Why do airplanes fly so high? Wouldn't it be shorter if they flew at low altitude? I mean... Earth is round, so it's smaller radius, therefore smaller length.

Does it have to do with air pressure?
gpt
It is all about efficiency, there is less air to plow through meaning you can fly faster with less fuel and the added benefit of avoiding most weather. 

Also the differences in distances traveled around the globe by being a few kilometers up are negligible. 

The Radius of Earth is 6,378 km

A jet airplane flys 11 km above the surface. 

* Circumference is 2pi * r

* Circumference of Earth = 2pi*6,378.1 = 40,074 km

* Circumference of Airplane flight = 2pi*6,389.1 = 40143 km


Even flying around the world it's only ~69 km (0.17%) longer a distance than the ideal surface distance.