The Antonov An-124 Ruslan is a large, strategic airlift, four-engined aircraft that was designed in the 1980s by the Antonov design bureau in the Ukrainian SSR of the Soviet Union (USSR). The An-124 is the world's second heaviest gross weight production cargo airplane and heaviest operating cargo aircraft, behind the destroyed one-off Antonov An-225 Mriya and the Boeing 747-8. The An-124 remains the largest military transport aircraft in service.

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.