Ya really. Hmm well if you REALLY need them. Open aircraft.cfg in FSEdit, find the location of the engines (under jet engines...

), write it down, and create a smoke file using these locations. That will make it look decent. If you want it better, make it about 5-10 feet behind the engine. More realistic. *shrug* Still don't think you need them but oh well. I do this on my high-flying turboprops as well (check out old pictures of really high level flying B-29s, etc., which have INCREDIBLE contrails way up there.