Thanks for the link to Lou's post... that was interesting. It sounds like Doppler navigation was the main form back then. Also, I looked at some pictures of 707-100 cockpits, and there is no INS system (at least not the kind that CS has used, so what's with that addition to the cockpit?!  :-?). I guess I'll read up on Doppler then, hopefully I can get it to work this time. Thanks for the prompt replies!  :)