President Trump is about to leave office for the last time as President, on a Marine Helicopter Squadron One Sikorsky VH-3D Sea King Helicopter with the callsign "Marine One" which left the White House for Joint Base Andrews as part of the departure ceremony.

Unlike previous handovers from old to new presidents, President Trump left the White House as President before his successor President Biden took office. In the past, it was common practice that the outgoing president would not leave the White House until the inauguration of the new president.

The presidential aircraft has a unique callsign: if the current president boards a Marine Corps helicopter, the aircraft’s callsign would become “#MarineOne”; when the president boards an Air Force aeroplane, the aeroplane’s callsign becomes the well known “#AirForceOne”.

The presidential helicopter fleet is operated by the Marine Corps's Marine Helicopter Squadron One, so "Marine One" has become synonymous with the presidential helicopter.

〖Outgoing President's Callsign - Executive One〗

When a former president leaves the White House, usually they are no longer the "current president" because they have inaugurated the new president so, when they board the Marine Corps Sea King helicopter, the callsign would no longer be "Marine One"; instead it would become "#ExecutiveOne".

When the outgoing president leaves on an Air Force aeroplane, he cannot use the "Air Force One" callsign, so the air force will use a special call sign: “Special Air Mission XX”. For example, the Air Force callsign when the 44th President Barack Obama left office was “Special Air Mission 44”.