At the end of the -80ies Mc Donnell Douglas looked at re-engineing the MD 80. Through studies the MD 80UDF (Unducted Fan) evolved, it featured a backmounted pusher system of several fans. The project didn't attract much attention from the airlines.

A more conservative aircraft design later evolved as the MD 90. It featured the highly fuel-efficient new generation International Aero Engine (IAE) V2500 engines and a 1,3m (4ft 6in) stretch forward of the wing. This raised the capacity by ten to 163 (two-class) or 172 (single-class). The aircraft incorporated the big tailplane of the MD 87, and the cockpit of the MD 87/88.

The MD 90 was the first Dc 9 derivative with a seating capacity of more than 150, thus making it a realistic replacement for aircraft like the Boeing 727.

The first MD 90 made it's maiden flight on February 22, 1993, with Delta as the first customer, followed by Saudia and Japan Air System. Deliveries continued to Air Aruba, China Eastern, China Northern, China Northern Swan, Reno Air (now flies for American Airlines after the latters takeover of Reno Air), SAS and Uni Airways Corporation.

Following the license assembly of 35 MD 82/83s, China's Shanghai Aircraft Manufacturing Factory signed up to build some 20 examples of the MD 90-30T Trunkliner, with a strengthened and modified dual main undercarriage from operations out of austere airfields in China. The program was however cancelled in mid 1998.

The extended range MD 90-30ER received it's launch order from AMC Aviation of Egypt in April 1997. These aircraft will operate in a 170 seat single-class layout. The -30ER featured additional fuel tanks and an increased MTOW (maximum take-off weight) of 5,450kg (12,000lb) to 76,270kg (168,144lb) (heavier than the 75,365kg [166,148lb] MD 90-30IGW delivered to Great China Airlines in March 1997), boosting range to more than 4,000km (2,150nm). Both the -30ER and the 30IGW featured a strengthened wing structure, undercarriage and flaps, with auxiliary tanks in the aft part of the forward cargo hold.

The proposed MD 90-50 would have been heavier, at 78,245kg (172,498lb), with 124.5kN (28,000lb) st V2528-D5 engines, carrying 153 passengers over extended ranges. An additional set of forward emergency exits would allow the otherwise simillar MD 90-55 to carry 187 passengers. The projects never materialized as Mc Donnell Douglas were taken over by Boeing, who decided to close the MD 80 and MD 90 production lines after fulfilling the orders. The last MD 90 was delivered to Saudi Arabian Airlines in February 2000.