Apparently the terrain is locked in a security catalog *.cat file. However there is some great information on terrain building at this site:
http://falcon4.nekromantix.com/terraintutorial.php
Best regards,
:shock:
Hehe... This is a step in the right direction (making all aircraft flyable, cockpits and loading screens for each). If somebody could work over the mission editor as well, that would be really cool...
:D