Aerial refueling, also referred to as air refueling, in-flight refueling (IFR), air-to-air refueling (AAR), and tanking, is the process of transferring aviation fuel from one military aircraft (the tanker) to another (the receiver) during flight. The two main refueling systems are probe-and-drogue, which is simpler to adapt to existing aircraft, and the flying boom, which offers faster fuel transfer, but requires a dedicated operator station.