Plan a flight route that always flys the same directions on your compass. For example East. Then keep flying in that direction until you end up at your starting point.
The Earth is a flat disk (like the pizza pie) and the compass needle always points to the center (north). This being so, if you travel east or west you will eventually travel in a circle.
And again, here we have the claim that, despite all of the cutting edge technology available to us, not a single person has ever figured out how to travel in a straight line.