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In the early days of aviation both the civil and military world, a practical method for traversing large distances was highly sought after. While airframe and engine designs were constantly evolving, air-to-air refueling was seen as the only immediate solution to the range extension problem, particularly for military applications.

The first attempts at air-to-air refueling were carried out as dangerous stunts performed by civilian pilots known as barnstormers at flying circuses. The first true systematic attempt of inflight refueling was conducted on October 3, 1920 in Washington D. Cabot of the United States Naval Reserve.
Finally, in 1923, WW I veteran pilots Captain Lowell Smith and Lieutenant John Richter, would devise a method to deal with the flight duration limits that plagued them during combat. A few months later, numerous test flights were flown over a circular course, with the team achieving their first flight endurance record on June 27th, at 6 hours and 39 minutes of flight time.

Using the refueling technique developed by Smith and Ricther, the tankers carried a 50 foot hose that would be lowered to the receiver aircraft, which itself was modified with a large fuel funnel that led to its fuselage tank. Throughout the entire flight, forty-two contacts were made with the tankers, with almost 5,000 gallons of gasoline and 245 gallons of oil being transferred.

By 1935, Cobham's would demonstrate a technique known as grappled-line looped-hose air-to-air refueling. In this procedure, the receiver aircraft would trail a steel cable which was then grappled by a line shot from the tanker. The line was then drawn into the tanker, where the receiver's cable was connected to the refueling hose. Once the hose was connected, the tanker climbed slightly above the receiving aircraft where fuel would flow under gravity. By the late 1930s, Cobham company, Flight Refuelling Ltd or FRL would become the very first producer of a commercially viable aerial refueling system.

In March of 1948, the USAF’s Air Material Command initiated the GEM program, in the hopes of developing long range strategic capabilities through the study of aircraft winterization, air-to-air refueling and advanced electronics. The air-to-air refueling program in particular was given top priority, within GEM. After a year of training and testing with the modified FRL air-to-air refueling system, it would be used by the B-50 Superfortress "Lucky Lady II" of the 43rd Bomb Wing to conduct the first non-stop around-the-world flight.

The solution to the problem came in the form of a flying boom refueling concept. The flying boom aerial refueling system is based on a telescoping rigid fueling pipe that is attached to the rear of a tanker aircraft. The entire mechanism is mounted on a gimbal, allowing it to move with the receiver aircraft. In a typical flying boom aerial refueling scenario, the receiver aircraft rendezvous with the tanker, and maintain formation.

The receiver aircraft then moves to an in-range position behind the tanker, under signal light or radio guidance from the boom operator. Once in position, the operator extends the boom to make contact with the receiver aircraft where fuel is then pumped through the boom.

Simultaneously, Boeing would develop the world's first production aerial tanker, the KC-97 Stratofreighter. . Over the next few years, these Boeing would develop the first high-altitude, high-speed jet-engine powered flying-boom aerial tanker, the KC-135 Stratotanker.

By 1949 Cobham had devised the first probe and drogue aerial refueling system. Probe-and-drogue refueling employs a flexible hose that trails behind the tanker aircraft. During aerial refueling, the drogue stabilizes the hose in flight and provides a funnel to guide the insertion of a matching refueling probe that extends from the receiver aircraft.

When refueling operations are complete, the hose can is then reeled up completely into an assembly known as the Hose Drum Unit. Operational testing of the first probe-and-drogue refueling system began in 1950.

On June 4th, 2021, The US Navy conducted its first-ever aerial refueling between a manned aircraft and an unmanned tanker, using a Boeing MQ-25 Stingray and a Navy F-18 Super Hornet. Conducted over Mascoutah, Illinois the 4 and half hour test flight performed a series of both wet and dry contacts with the UAV, with a total of 10 minutes of total contact time and transferring around 50 gallons of fuel.


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