Here is my experience of flying to the edge of the practice map:
Once you get past where the minimap is there is a bit more terrain with hills and trees. After that there is no foliage and no terrain features except for a few lakes towards the end. After that I crossed into just sky, and could see a rectangular landmass behind me. After quite some more time, I was approaching an end to the sky where it looked like there might be another landmass. Unfortunately the game made me get out of the plane and then I parachuted for a long time in the sky, eventually “successfully landing” and returning to spawn. This isn’t really that important but I thought it was interesting
