McDonnell Douglas MD-12

 In late 1991, McDonnell Douglas made a move to separate its civil and military divisions in a bid to raise the estimated $4 billion development costs needed to develop the MD-12X trijet. Separating the costly military C-17 airlifter development, which had been a drain on the company's resources, from the profit-making production of the MD-80 and MD-11 airliners would make it easier to attract foreign investors for the MD-12X.^[4]

McDonnell Douglas unveiled its MD-12 design in April 1992.^[3] The design was similar in concept to the Airbus A3XX and Boeing NLA, and it would have been larger than theBoeing 747 with which it would have directly competed. Douglas Aircraft had also studied a smaller double-decker design in the 1960s.^[5][6]

The first flight of the MD-12 was to take place in late 1995, with delivery in 1997.^[3] Despite aggressive marketing and initial excitement, especially in the aviation press, no orders were placed for the aircraft. MDC lacked the resources after Taiwan Aerospace left the project.^[3] A new double deck widebody has proved to be extremely expensive and complex to develop, even for the remaining aerospace giants Boeing and Airbus, although the massive Airbus A380, a similar concept to the MD-12, was later brought to fruition.

The design grew into the much larger MD-12 with four engines and two passenger decks extending the length of the fuselage. The length of the main MD-12 variants was 208 ft (63.4 m) with a wingspan of 213 ft (64.9 m). The fuselage was 24 ft 3 in (7.39 m) wide by 27 ft 11 in (8.51 m) high.

With the MD-12 program over, McDonnell Douglas focused on 300 to 400–seat MD-11 derivatives. At the 1996 Farnborough International Air Show, the company presented plans for a new trijet with high-seating and long-range named "MD-XX".^[9] The MD-XX was offered in two variants; MD-XX Stretch with a longer fuselage and MD-XX LR for longer range. Both MD-XX variant designs had 213 ft (64.9 m) wingspan, the same as MD-12. The MD-XX Stretch was lengthened 32 ft (9.8 m) over the MD-11 and had seating for 375 in a typical 3-class arrangement and 515 in all-economy seating. Its range was to be 7,020 nmi (8,080 mi; 13,000 km). The MD-XX LR was the same length as the MD-11, had seating for 309 in a typical 3-class arrangement and featured a range of 8,320 nmi (9,570 mi; 15,400 km). However, the MDC board of directors decided to end the MD-XX program in October 1996, stating the financial investment for the program was too large for the company