Dennis, VC-25's 82-8000 and 82-9000 are both used as Air Force 1. One is used as AF1 and the other is usually tagging along as a back up. When not carrying the POTUS they use the SAM designator. Today SAM 28000 was the back up aircraft. He landed at Andrews in the late-1800 hour EDT about 35 minutes before Air Force 1 touched down. RON MARYLAND, USA