You can fly outside of the 1000x1000km box. You can't spawn outside of the box. If you set up your spawn point outside the box, the game puts you on mission start at the closest edge of the box to the spawn point you made. During the mission you can fly outside of the box, and your map seems to be there.
sputnikshock, you might be right... it has to do with the waypoint coordinate system, not a stock limitation. I think the game can not "read", for airplanes, more than 1000x1000 in coordinates. All your waypoints appear in the in-flight map bunched up at the closest edge.
Maybe there is a way to expand this 1000x1000 limit to, say, a 3000x3000 limit without actually changing the "game engine" to eliminate the limit? Or tricking the game to think you are still inside the box? Becuase the map outside the box is there and you can fly to it... it is just the spawning and waypoints that is limited to the box.
I love megamaps! I got tired of waiting for mapmakers to do them, so I decided to start making my own this past winter... so I am a "newbie" on this. But so far I have made five 1:1s: Guadacanl-Rabaul, Sicily/South Italy-Malta-North Africa-Tripoli, Okinawa-Hiroshima-Nagasaki-Osaka, The Taiwan area, and Southern China.
I'll post an image of the Guadacanal-Rabaul if you tell me how, I have no idea how to do it. These maps are huge in file size, so I dont' know how to share them. But once they are finished (with all the actors, ect) I'll post them if I know how.