Ok, this was beat to death in the "B-billets" thread. Suffice it to say that there is a good chance you could get sent to the ground side. However, HQMC is reviewing the whole FAC thing per the June issue of the Marine Corps Gazette (I am still trying to get my hands on it to read the full story.). What happens is that after your initial tour (could be 3,4,5,6 years in your primary billet, you will rotate out to a B-billet. EVERYBODY. 46pilots, Harrier pilots, C-130 pilots, infantry officers, Motor-T officers, everybody. That B-Billet could be a flight school instructor, TBS instructor, FAC tour, MEU staff tour, EWS student, etc. However, if you go to the reserves, you generally stay with your unit until you get promoted out of a billet - thus guys are at a reserve C-130 unit, a reserve CH-46 unit until they pin on LtCol which could be 5 to 8 years. In my case, I was winged in '92 and have never been out of the cockpit - even though I tried to get Naval Attache tours.
Hope this helps.