President: Richard Nixon, Gerald Ford, Jimmy Carter, Ronald Regan, George H. W. Bush, Bill Clinton, George W. Bush

Kennedy's Boeing was starting to show its age, so Nixon replaced it in 1972 with a newer 707 that bore the call-sign, when not carrying the president, SAM-27000. After Nixon's resignation, Col. Ralph Albertazzie, the pilot, famously said to Kansas City Air Traffic Control "Kansas City, this was Air Force One. Will you change our callsign to SAM-27000?" as the man on board was no longer the President. 

Although newer planes were purchased in 1990, SAM-27000 stayed active as a back-up until 2001, when it took George W. Bush to Waco, TX.