When playing for the first time, a simple pop up tutorial would be nice, explaining what to do. Figuring out how to land and how to drag the planes takes a second, but it is fine. However, I still haven't figured out what to do with starting planes? I can't change their route, so how do I prevent two starting planes from crashing?

Edit: I would also add some “crash margin” around the border of the screen. A plane coming from the top right corner and crashing into a plane leaving just to the right of the top right corner is frustrating.