Is this with 3rd party missions? Some don't have the Advanced Info option enabled which will cause this problem. Read the install instructions carefully as you might need to add an entry to airbases.dat.
Providing you installed the 3rd party scenery separately & activated it via the Scenery Library try deactivating it. That should fix the problem. If you pasted (or unzipped) the files direct to CFS2, you might have a problem. Unless you know which files you pasted where & can remove them the only way out might be a full Uninstall/Install of CFS2. Read my CFS2 FAQ page first.
http://www.simviation.com/lair/cfs2faq.htmIf you do this please move any 3rd party aircraft you wish to keep. Also back up the CFS2\Gauges folder.