The Douglas DC-8 is an early long-range narrow-body jetliner designed and produced by the American Douglas Aircraft Company. Work began in 1952 towards the United States Air Force's (USAF) requirement for a jet-powered aerial refueling tanker. After losing the USAF's tanker competition to the rival Boeing KC-135 Stratotanker in May 1954, Douglas announced in June 1955 its derived jetliner project marketed to civil operators. In October 1955, Pan Am made the first order along with the competing Boeing 707, and many other airlines soon followed. The first DC-8 was rolled out in Long Beach Airport on April 9, 1958, and flew for the first time on May 30. Following Federal Aviation Administration (FAA) certification in August 1959, the DC-8 entered service with Delta Air Lines on September 18.

A four-engined jet, sometimes called a quadjet, is a jet aircraft powered by four engines. The presence of four engines offers increased power, allowing such aircraft to be used as airliners, freighters, and military aircraft. Many of the first purpose-built jet airliners had four engines, among which stands the De Havilland Comet, the world's first commercial jetliner. In the decades following their introduction, their use has gradually declined due to a variety of factors, including the approval of twin-engine jets to fly farther from diversion airports as reliability increased, and an increased emphasis on fuel efficiency.