The DC-8 was the first Douglas jet-powered transport. It entered service simultaneously with United Airlines and Delta Air Lines on Sept. 18, 1959. Powered by four jet turbine engines, the DC-8 was capable of speeds of more than 600 mph (966 km/h). In a test dive, it became the first commercial transport of any kind to break the sound barrier. Throughout its 14-year-long production run, the DC-8 went through seven major variants, for a total of 556 aircraft.

The basic domestic version, the DC-8 Series 10, had increased fuel capacity for intercontinental flights, and the Series 30 and 40 were the first to use the 17,500-pound-thrust (7938-kilogram-thrust) turbojet engines.

The DC-8 Series 50 were the first DC-8s powered by new, more efficient turbofan jet engines with 18,000 pounds (8165 kilogram) thrust and longer range. The Series 50 were also the first to be offered customers in the convertible passenger-freight version or the windowless all-freight version.

The DC-8 Series 60 extended the length of the fuselage. Nearly 37 feet (11 meters) longer than the original model, in an all-economy passenger configuration, the DC-8-61 could carry 259 people. Its convertible-freighter configuration had a cargo volume of 12,535 cubic feet (3820 cubic meters). The DC-8-62, for extra-long routes, had a fuselage stretched 6 feet 8 inches (2 meters) longer than the original model and 3-foot (91-centimeter) wingtip extensions.

All design improvements of the DC-8-61 and -62 were incorporated in the DC-8-63. The -63 could fly more than 4,500 miles (7242 kilometers) nonstop, carrying 259 passengers because of its extended fuselage; aerodynamic improvements to nacelles, pylons and flaps; and increased wingspan and fuel capacity.

The DC-8 Series 70 was a re-engined version of the popular Super 60 Series, substituting CFM56 engines for the latter’s Pratt & Whitney engines. The result was an aircraft that retained the Super 60 operating weights but with a longer range due to the newer, more fuel-efficient turbofans. The Series 70 was also able to meet later, more stringent noise regulations that were implemented in the 1980s.

In 1995, more than 300 DC-8s remained in service, making more than 340 scheduled flights a day. In January 2013, Aviation Week Intelligence Network’s Fleet Database reported that there were 36 DC-8s left in service worldwide.