Terrain on the flight. The one I used was the story trigger one they sent me on, I think it was to the second town in the list? My save is a bit out in the middle of nowhere, but I can check later tonight to get the actual route. It only clipped for a very short bit into one of those tall post like mountain shapes. Didn't do anything besides look graphically a little odd.
I'll jot down coordinates from now on if I find other oddities. I guess you might also need the version too, since the game is generated?