Some of the earliest experiments in in-flight refueling took place in 1923, using a hose to transfer fuel from a hand-held fuel tank on one aircraft to the usual fuel filler of the second. However, the first practical in-flight refueling system was not demonstrated until 1935, by Alan Cobham's Flight Refuelling Ltd. Known as the grappled-line looped-hose system, it was intended to be used to refuel heavy bombers in the Far East during World War II but the war ended before it could be used. After the war, Flight Refuelling Ltd would go on to develop the probe and drogue system still used for in-flight refueling today by the RAF as well as the US Navy, US Marines, most Western European military aircraft and Russian military aircraft as well. In this book, noted aviation expert and in-flight photographer Keith Wilson explores the history and development of in-flight refueling, one of the most delicate processes a pilot can undertake.