The story of air refueling begins in the 1920s when bold pilots attempted to refuel their airplanes while in flight. On 2 Oct 1921, a HD-4 biplane flew down the Potomac River while the crew used a grappling hook to attempt to snatch a five-gallon gasoline can from a float. Almost two months later on 21 Nov 1921 a wing walker climbed from one biplane to another, braving cold and high winds, with a five-gallon gas can strapped to his back. This publicity stunt is generally accepted as the first air-to-air refueling.
As time passed, air refueling became safe and efficient. Today the Air Mobility Command's KC-10s and KC-135s refuel aircraft like the C-17s and C-5s stationed at Dover AFB.
Our air refueling timeline located on the hangar mezzanine will tell you the whole story.