alt Hacker NewsFlying up too high becomes quite interesting. Eventually you hit the point where you're missing the ground and end up on an upward spiral... essentially falling up. You have to go backward to find a place where you can start falling down back toward the ground.
This could be fixed by adding a barrier at a high enough altitude. A firmament if you will. This would allow the minecraft map to appear round, when we all know it's really flat...