Pretty sure the only FAA reg which specifically mentions seatbelts and which is applicable to passengers is found in part 91 and only requires you to wear the seatbelt when taxying, take off, landing.
Aha, got a bit more..
121.317
(f) Each passenger required by §121.311(b) to occupy a seat or berth shall fasten his or her safety belt about him or her and keep it fastened while the "Fasten Seat Belt" sign is lighted.
So there you go....
Last edited by Scumbag O'Riley; 14th December 2009 at 08:54.