I've seen several articles on Mrs. O's trip all making reference to the aircraft she was on as Air Force 2 as the conventrional wisdom for the designation of the presidential Air Force 1 back-up.
From FAA instructions:
7. Presidential aircraft and Presidential family aircraft:
(a) When the President is aboard a military aircraft, state the name of the military service, followed by the word “One.”
EXAMPLE-
“Air Force One.”
“Army One.”
“Marine One.”
(b) When the President is aboard a civil aircraft, state the words “Executive One.”
(c) When a member of the President’s family is aboard any aircraft, if the U.S. Secret Service or the White House Staff determines it is necessary, state the words “Executive One Foxtrot.”
Yes, in 1973 Nixon flew on a United Airlines flight during the gas shortage and used Executive One.
Twice there has been a Navy One, when Nixon flew to the carrier for the Apollo 11 splashdown, and when Bush flew to the carrier in an S-3. In Navy tradition, an arriving commander is announced by his unit of command, e.g., “Sixth Fleet” or “149th Air Wing”. For Bush and Nixon, it was “United States of America coming aboard”.
I've seen several articles on Mrs. O's trip all making reference to the aircraft she was on as Air Force 2 as the conventrional wisdom for the designation of the presidential Air Force 1 back-up.