Listening to the popular press has caused many people to believe "Air Force
One" is an airplane, when in fact it is just a radio callsign. It is the
callsign of any USAF airplane that has the president aboard, and at times an
aircraft other than one of the two VC-25s (747-200) assigned to the 89th AW
is used. The 89th AW also operates the C-37, a military version of the
Gulfstream 5.

Actually, I thought *any* plane with the President on board became, de facto,
"Air Force One"!

I don't think we've seen an accurate version of this story yet. They
deliberately filed a wrong aircraft type as a security measure?
Makes sense to me! You have to worry about "Gomer Al-Pyle, (Former) Republican
Guard"
with his Stinger/"Grail", (Soviet man-portable anti-aircraft missile/RPG;
*after all*!

What did they file as the callsign? If they filed as Air Force One they
defeated the purpose of filing the wrong type aircraft. If they filed as
SAM1234, then the UK controller would have no aircraft on frequency or any
flight plan data on Air Force One. So when the question was asked, "is that
Air Force
One", what was the controller looking at to determine it was a Gulfstream 5?