Originally Posted by
Cloudship
When traveling domestically, the president often uses the C-32 (757) or one of the helicopters. The 747 is a bit overkill for short haul travel.
Theoretically any aircraft he is on is Air Force One, but in practice they dedicate specific equipment just to his (or her) use.
any idea why he was in Providence?
No, he doesn't "often use" the C-32 unless the runway can't accommodate the VC-25 (747) or even more rarely, if both VC-25s are unavailable for some reason. The VC-25 is used even for short domestic hops (Andrews AFB to Wright-Patterson AFB, <300 miles or so, for one example). The Marine One helicopters are primarily for very short local travel, like transport to/from the White House and Andrews.
The C-32 doesn't have the full range of equipment, accessories, and other things the VC-25 does, making it less than ideal for transport of the President. and is only sparingly used for such. The C-32 is primarily used by the Vice President, Secretary of State, and on occasion others.
Preliminary plans are in work for a replacement to the VC-25.
The call sign Air Force One isn't just theoretical, it is standard practice that any US Air Force aircraft carrying him operates under than call sign while the President is onboard.