It takes precision and great pilot skills to refuel airplanes in midair. 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 boom operator station. The procedure allows the receiving aircraft to remain airborne longer, extending its range or loiter time on station. A series of air refueling can give range limited only by crew fatigue and engineering factors such as engine oil consumption. Because the receiver aircraft can be topped up with extra fuel in the air, air refueling can allow a takeoff with a greater payload which could be weapons, cargo, or personnel: the maximum takeoff weight is maintained by carrying less fuel and topping up once airborne.
The Dangerous Business of Aerial Refueling