Luis,Thanks for the quick reply, I'm using the simmer's sky scenery for narita so I think the problem is related to that. The scenery does have photoscenery surrounding the airport which would normally exclude autogen, however I used a program called Auto trees to fill in the photoscenery with trees. This solved the problem further away from the airport but as soon as you get near the airport the trees disappear. I think it may be one of those scenery packages that have very large exclude zones. Do you have any idea how to make these smaller?