The Douglas DC-8 (sometimes McDonnell Douglas DC-8) is a long-range narrow-body airliner built by the American Douglas Aircraft Company. After losing the May 1954 US Air Force tanker competition to the Boeing KC-135, Douglas announced in July 1955 its derived jetliner project. In October 1955, Pan Am made the first order along with the competing Boeing 707, and many other airlines 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. FAA certification was achieved in August 1959 and the DC-8 entered service with Delta Air Lines on September 18.

The six-abreast, low wing airliner was a four-engined jet aircraft with initial variants being 151 ft (46 m) long. The DC-8-10 was powered by Pratt & Whitney JT3C turbojets and had a 273,000 lb (124 t) MTOW, the DC-8-20 had more powerful JT4A turbojets for a 276,000 lb (125 t) MTOW. The intercontinental models had more fuel capacity and up to 315,000 lb (143 t) MTOW, powered by JT4As for the Series 30 and by Rolls-Royce Conway turbofans for the Series 40. The Pratt & Whitney JT3D powered the later DC-8-50 and Super 60 (DC-8-61, -62, and -63) as well as freighter versions, and reached a MTOW of 325,000 lb (147 t).

The improved Series 60 was announced in April 1965. The DC-8-61 was stretched by 36 ft (11 m) for 180–220 seats in mixed-class and a MTOW of 325,000 lb (147 t). It first flew on March 14, 1966, was certified on September 2, 1966, and entered service with United Airlines in February 1967. The long-range DC-8-62 followed in April 1967, stretched by 7 ft (2.1 m), could seat up to 189 passengers over 5,200 nmi (9,600 km) with a larger wing for a MTOW up to 350,000 lb (159 t). The DC-8-63 had the long fuselage and the enlarged wing, freighters MTOW reached 355,000 lb (161 t).

The DC-8 was produced until 1972 with 556 aircraft built. It was superseded by larger wide-body airliners including Douglas' DC-10. In 1975, the Series 70 retrofit was proposed with the quieter and more fuel-efficient CFM56 turbofan. Some re-engined freighters are still in use.

The McDonnell Douglas DC-9 is an American five-abreast, single-aisle aircraft designed by the Douglas Aircraft Company. It was initially produced by the developer company as the Douglas DC-9 until August 1967 and then by McDonnell Douglas. After introducing its heavy DC-8 in 1959, Douglas approved the smaller, all-new DC-9 for shorter flights on April 8, 1963. The DC-9-10 first flew on February 25, 1965, and gained its type certificate on November 23, to enter service with Delta Air Lines on December 8. The aircraft has two rear-mounted Pratt & Whitney JT8D low-bypass turbofans under a T-tail for a cleaner wing aerodynamic, a two-person flight deck, and built-in airstairs.

The Series 10 aircraft are 104 ft (32 m) long for typically 90 coach seats. The Series 30, stretched by 15 ft (4.5 m) to seat 115 in economy, has a larger wing and more powerful engines for a higher maximum takeoff weight (MTOW); it first flew in August 1966 and entered service in February 1967. The Series 20 has the Series 10 fuselage, more powerful engines, and the Series 30's improved wings; it first flew in September 1968 and entered service in January 1969. The Series 40 was further lengthened by 6 ft (2 m) for 125 passengers, and the final DC-9-50 series first flew in 1974, stretched again by 8 ft (2.5 m) for 135 passengers. When deliveries ended in October 1982, 976 had been built. Smaller variants competed with the BAC One-Eleven, Fokker F28, and Sud Aviation Caravelle, and larger ones with the original Boeing 737.

The original DC-9 was followed by the second generation in 1980, the MD-80 series, a lengthened DC-9-50 with a larger wing and a higher MTOW. This was further developed into the third generation, the MD-90, in the early 1990s, as the body was stretched again, fitted with V2500 high-bypass turbofans, and an updated flight deck. The shorter and final version, the MD-95, was renamed the Boeing 717 after McDonnell Douglas's merger with Boeing in 1997; it is powered by Rolls-Royce BR715 engines. The DC-9 family was produced between 1965 and 2006 with a total delivery of 2441 units: 976 DC-9s, 1191 MD-80s, 116 MD-90s, and 155 Boeing 717s. As of August 2022, 250 aircraft remain in service: 31 DC-9s (freighter), 116 MD-80s (mainly freighter), and 103 Boeing 717s (passenger), while the MD-90 was retired without freighter conversion.

The McDonnell Douglas DC-10 is an American trijet wide-body aircraft manufactured by McDonnell Douglas. The DC-10 was intended to succeed the DC-8 for long-range flights. It first flew on August 29, 1970; it was introduced on August 5, 1971, by American Airlines.

The trijet has two turbofans on underwing pylons and a third one at the base of the vertical stabilizer. The twin-aisle layout has a typical seating for 270 in two classes. The initial DC-10-10 had a 3,500 nmi (6,500 km) range for transcontinental flights. The DC-10-15 had more powerful engines for hot and high airports. The DC-10-30 and −40 models (with a third main landing gear leg to support higher weights) each had intercontinental ranges of up to 5,200 nmi (9,600 km). The KC-10 Extender (based on the DC-10-30) is a U.S. Air Force tanker.

A design flaw in the original cargo doors caused a poor safety record in early operations. Following the American Airlines Flight 191 crash (the deadliest aviation accident in US history), the US Federal Aviation Administration (FAA) grounded all U.S. DC-10s in June 1979. In August 1983, McDonnell Douglas announced that production would end due to a lack of orders, as it had a widespread public apprehension after the 1979 crash and a poor fuel economy reputation. Design flaws were rectified and fleet hours increased, for a safety record later comparable to similar era passenger jets.

Production ended in 1989, with 386 delivered to airlines along with 60 KC-10 tanker aircraft. The DC-10 outsold the similar Lockheed L-1011 TriStar. It was succeeded by the lengthened, heavier McDonnell Douglas MD-11. After merging with McDonnell Douglas in 1997, Boeing upgraded many in-service DC-10s as the MD-10 with a glass cockpit that eliminated the need for a flight engineer. In February 2014, the DC-10 made its last commercial passenger flight. Cargo airlines continue to operate a small number as freighters. The Orbis Flying Eye Hospital is a DC-10 adapted for eye surgery. A few DC-10s have been converted for aerial firefighting use. Some DC-10s are on display, while other retired aircraft are in storage.

The McDonnell Douglas MD-11 is an American tri-jet wide-body airliner manufactured by American McDonnell Douglas (MDC) and later by Boeing. Following DC-10 development studies, the MD-11 program was launched on December 30, 1986. Assembly of the first prototype began on March 9, 1988. It rolled out in September 1989 and made its maiden flight on January 10, 1990. FAA certification was achieved on November 8. The first delivery was to Finnair on December 7, 1990, and it entered service on December 20.

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It retains the basic trijet configuration of the DC-10 with updated GE CF6-80C2 or PW4000 turbofan engines. It has a slightly wider wing with winglets, and its MTOW was increased by 14% to 630,500 lb (286 t). Its fuselage is stretched by 11% to 202 ft (61.6 m) to accommodate 298 passengers in three classes over a range of up to 7,130 nmi (13,200 km). It features a glass cockpit that eliminates the need for a flight engineer. The MD-11 failed to meet its range and fuel burn targets. The last of 200 aircraft was built in October 2000 after Boeing merged with McDonnell Douglas in 1997. Some MD-11 freighters were built, but many more are converted MD-11 passenger aircraft, many of which are still in service with cargo airlines.

The McDonnell Douglas (later Boeing) MD-90 is an American five-abreast single-aisle airliner developed by McDonnell Douglas from its successful model MD-80. The airliner was produced by the developer company until 1997 and then by Boeing Commercial Airplanes. It was a stretched derivative of the MD-80 and thus the third generation of the DC-9 family. After the more fuel-efficient IAE V2500 high-bypass turbofan was selected, Delta Air Lines became the launch customer on November 14, 1989. The MD-90 first flew on February 22, 1993, and the first delivery was in February 1995 to Delta.

The MD-90 competed with the Airbus A320ceo family and the Boeing 737 Next Generation. Its 5 ft (1.4 m) longer fuselage seats 153 passengers in a mixed configuration over up to 2,455 nmi (4,547 km), making it the largest member of the DC-9 family. It kept the MD-88's electronic flight instrument system (EFIS). The shrunken derivative of MD-80 or shorter variant of MD-90, originally marketed as MD-95, was later renamed the Boeing 717 following McDonnell Douglas' merger with Boeing in 1997. Production ended in 2000 after 116 deliveries. Delta Air Lines flew the final MD-90 passenger flight on June 2, 2020, marking the retirement of the type. It was involved in three hull-loss accidents with only one fatality being a fire related or non-aeronautical accident.