Aerial Refueling

Aerial refueling is the process of transferring aviation fuel from one aircraft, the tanker, to another, the receiver, while both remain in flight, most commonly through one of two systems: probe-and-drogue, which is simpler to fit to an existing aircraft, and the flying boom, which transfers fuel faster but needs a dedicated boom operator. By letting a receiving aircraft carry less fuel at takeoff and top up in the air, aerial refueling extends range or loiter time and increases usable payload, with a series of refuelings limiting an aircraft's endurance mainly by crew fatigue rather than fuel alone. Early experiments took place in the 1920s among slow-flying aircraft, and the first mid-air transfer of fuel between two aircraft took place on June 25, 1923, between two Airco DH-4B biplanes of the United States Army Air Service, building on development work by Alexander P. de Seversky; the technique saw limited use before the Second World War on British civilian transatlantic flying boats, then large-scale use afterward for strategic bombers, and has been used exclusively in military operations, extensively since the Vietnam War.