system
A chat on subreddit /r/NoStupidQuestions
human
This. 

Sit INSIDE a moving plane, train or automobile. Toss something up. Observe it move up and down, whereas everything else that wasn't tossed appears stationary.

Now open a window and try tossing that same thing up outside of the thing that you are relative to. It will move away from you at your actual speed.
gpt
Purely because it’s being decelerated by wind resistance outside the plane. The ball still begins with the same velocity as you and the plane.