After the more fuel-efficient IAE V2500 high-bypass turbofan was selected, Delta Air Lines became the launch customer on November 14, 1989.

Its 5 ft (1.4 m) longer fuselage seats 153 passengers in a mixed configuration over up to 2,455 nautical miles [nmi] (4,547 km; 2,825 mi), making it the largest member of the DC-9 family.

The MD-90, the stretched derivative of the MD-80 and thus the third generation of the DC-9 family,[citation needed] was launched on November 14, 1989 when Delta Air Lines placed an order for 50 MD-90s, with options to purchase a further 110 aircraft.

[11] Powered by the 26,500 lbf thrust (118 kN) CFM56-5 or V2500, the MD-90X replaced the MD-89 as McDonnell Douglas's proposed new turbofan offering, and it was designed to compete with the Boeing 757.

[12] For several years, McDonnell Douglas proposed powering the MD-90 with two unducted fan (UDF) or propfan engines,[13] designated the MD-94X.

[14] By mid-1989, it was clear that there was insufficient interest in propfan-powered aircraft, so the company reworked its proposals to instead feature the IAE V2500 turbofan,[8][15] which was estimated to be $1 million cheaper than the GE36 and had already been certified for the Airbus A320.

[17] When the United States Navy wanted to replace its 125 Lockheed P-3 Orion anti-submarine warfare (ASW) aircraft, McDonnell Douglas offered the P-9D, which would be a propfan-powered version of the MD-91.

In 1991, McDonnell Douglas revealed that it was again considering developing a specialized 100-seat version of the MD-80, to be some 8 ft (2.4 m) shorter than the MD-87, powered with engines in the 16,000–17,000 lbf (71–76 kN) thrust class.

[19][page needed] At the Paris Airshow, McDonnell Douglas announced the development of a 105-seat version of the MD-80, designated MD-95.

At this time, McDonnell Douglas said that it expected the MD-95 to become a family of aircraft with the capability of increased range and seating capacity.

The MD-95 was a complete overhaul, going back to the original DC-9-30 design and applying new engines, cockpit and other more modern systems.

However, as with the MD-80SF, the narrow fuselage cross-section only allows for non-standard 88" x 108" pallets or containers, which is the main disadvantage in cargo operations and limits its potential market.

The main reason for AEI's decision not to continue the 13-pallet freighter program was the limited availability of MD-90 in the market.

[29] On June 2, 2020, Delta operated its last MD-90 on the type's final commercial flights,[30][31] and so the MD-90 was retired without a freighter conversion to extend its service life.

The −30ER has a higher gross weight and range up to 2,455 nmi (4,547 km; 2,825 mi) with an extra 565 US gal (2,140 L) auxiliary fuel tank.