<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by hfly:
You did not see AF1, you saw a VC-25 (There are two of them). At the same time AF may have been a modified business jet, fighter jet, or any other fixed wing a/c that the President was on. If he were on a rotary a/c it would have been (I believe) Marine One.</font>
Actually, no, it has nothing to do with the type of aircraft but only who is operating the aircraft.
Since the Air Force generally transports him, that's where the name "Air Force One" comes from. "Marine One" is operated by the Marines. If he was on an Navy aircraft, it would be "Navy One."
A non-military aircraft (private, airliner, etc) would be "Executive One"
VP has "Air Force Two," "Marine Two," "Executive Two," etc.