>>Airforce One is a PASSENGER, not an airplane, and if I read pprune later, I would be pretty embarrassed at having revealed my ignorance.<<
Well, don't worry about your ignorance <g> but actually Air Force One is the callsign of a U.S. Air Force plane carrying the President. I think this is what you were saying. And the current livery with "United States of America" on the side that you mentioned was originally approved during the Kennedy administration.
If you catch AF1 on the ground doing clear voice preflight HF radio checks with Crown (the White House Communications Agency), the radio operator will use SAM 28000 (or whatever) until the President boards. At that time, the radio operator will make the traditional announcement "SAM 28000 is now Air Force One".
________________________________________
Some online references:
"...When the President of the United States is aboard either aircraft, or any Air Force aircraft for that matter, the radio call sign is "Air Force One". "
http://www.theaviationzone.com/factsheets/c25.asp
"...Among the most important military callsigns, there is of course "Air Force One", which identifies any aircraft carrying the President of the United States. In the case of a [Marine]helicopter, it becomes "Marine One". Other presidential callsigns include "Air Force Two" for the Vice President, and "Executive Foxtrot One" for the First Lady. "
http://www.airodyssey.net/reference/radiocomm.html
"...Air Force One is the callsign of any United States Air Force aircraft carrying the President of the United States of America. "
http://en2.wikipedia.org/wiki/Air_Force_One
And, the S-3B that President Bush rode aboard the USS Abraham Lincoln had a callsign of "Navy One":
http://www.thesunlink.com/redesign/2...l/136651.shtml