Air Force Three is the air traffic control designated call sign held by any United States Air Force aircraft carrying the United States secretary of state, but not the president of the United States or vice president. The term is often associated with the Boeing C-32, a modified 757 which is most commonly used as the secretary of state's transport.

In July 1955, John Foster Dulles became the first Secretary of State to fly internationally on an American government airplane, travelling aboard Columbine III to Geneva, Switzerland, alongside President Dwight D. Eisenhower.

From the tenures of Henry Kissinger to Warren Christopher, the secretary of state's official aircraft was a modified Boeing 707.

The C-20 Gulfstream was used as an alternate Air Force Three during the tenure of Secretary George Shultz.

During James Baker's tenure, the secretary of state flew aboard a VC-137C SAM 26000, after the presidential plane was upgraded in 1990.

Since the tenure of Secretary Madeleine Albright, the Boeing C-32 has been the primary aircraft of the secretary of state.

During the tenure of Hillary Clinton as Secretary of State, Air Force Three flew to 112 countries, the most of any Secretary of State in U.S. history.

Aircraft allocated for use by the secretary of state and senior executives authorized to travel under the Special Air Mission designation operated by the 89th Airlift Wing can be distinguished from the distinctive Raymond Loewy Air Force One livery by the lack of the steel blue   cheatline and cap over the cockpit.