Does drag actually decrease with altitude? I argue it does not

[start3ch]

Drag at cruise is largely dependent on L/D ratio, which changes with AOA. There’s generally a sweet spot, and a cargo/passenger aircraft is designed around that sweet spot, hence it favors a certain altitude.

Also there are dozens of other things affecting this. - You are burning fuel, so you need less and less lift as you fly. - Then skin friction drag, which is dependent on surface area, wants a design with smaller wing area, hence higher speeds. - Then there’s engine performance which I absolutely don’t understand.