The Boeing 367-80, known as the “Dash 80,” led to both the Boeing 707 airliner and the KC-135 tanker.
Boeing built the prototype as a private demonstration aircraft to prove that swept-wing jet transports could be commercially viable. It rolled out in 1954 and made its first flight on July 15 that year, giving Boeing a foundation for its first successful jet-powered airliner program.
The Dash 80 was not itself a regular production airliner. Instead, its design was developed into two closely related aircraft: the Boeing 707 for airlines and the Boeing KC-135 Stratotanker for the United States Air Force. Their fuselages differed, because the military tanker required a wider cabin and other specialized features.
The prototype also became famous for a dramatic 1955 barrel roll performed by Boeing test pilot Alvin “Tex” Johnston over Lake Washington during a demonstration. The maneuver impressed spectators but reportedly startled Boeing president Bill Allen. The preserved aircraft is now displayed at the Smithsonian’s National Air and Space Museum.