Help! Objects are disappearing in FS

[Auriga]

I put several GMAX created objects into Microsoft Flight Sim 2002. The problem is that sometimes as I fly toward an object it disappears. Sometimes it reappears, sometimes not. I thought it would help to apply color. I did this by doing a drag-and-drop from the material navigator (is that as good as applying color from the material editor?). It didn't work; the objects still disappear. Would it help to apply texture too? Where do i get textures from?

Does anyone have any ideas on what else could be causing this and how to fix it?

Thank you very much.