Thank you for your test & time.
As I suspected, something is missing from your pc for the mission to run. I mean some element of the mission is not there. And it can be one of either : 3d ground crew, f-18 omar skin or the ufo. This is Free Flight, though you opened it from Missions Menu.

Only thing I can think of, is that you have not placed 3d ground crew in Add On scenery of FSX. (I mean the contents of texture & scenery folders found in folder "3d us ground crew", inside the corresponding folders of Add On Scenery).