McDonnell Douglas MD-94X

The McDonnell Douglas MD-94X was a planned propfan-powered airliner, intended to begin production in 1994. Announced in January 1986, the aircraft was to seat between 160 and 180 passengers, possibly using a twin-aisle configuration. An all-new design that was investigated internally since at least 1984, the MD-94X was developed in the mid-1980s to compete with the similar Boeing 7J7. The price of oil would have to be at least US$1.40 per gallon for McDonnell Douglas to build the plane, though. Configuration was similar to the MD-80, but advanced technologies such as canard noseplanes, laminar and turbulent boundary layer control, side-stick flight control (via fiber optics), and aluminum-lithium alloy construction were under consideration. Airline interest in the brand-new propfan technology was weak despite claims of up to a 60% reduction in fuel use, and both aircraft were canceled.

Under development at the same time were two propfan-powered commercial variants of the MD-80. The "MD-91X" would have seated 100-110 and entered service in 1991. The "MD-92X," a 150-seat aircraft targeted for service entry in 1992, was originally to be a 76 in of the MD-80. The price per engine would have been an estimated US$1.6 million dollars more for the propfans than for the MD-80's Pratt & Whitney JT8D-200 series engines. Existing DC-9s and MD-80s would also have been eligible for an upgrade to the new propfan powerplants. On May 19, 1987, McDonnell Douglas tested General Electric Aviation's unducted fan (UDF) engine in flight for the first time on an MD-80 demonstrator, an aircraft that was restored after suffering an empennage separation in 1980 during the landing of a certification test flight for the DC-9 Super 80.

A propfan-powered military variant of the MD-87 or MD-91X, called the P-9D, was also proposed as an anti-submarine warfare (ASW) aircraft. The P-9D was intended for use in the United States Navy's Long Range Air ASW-Capable Aircraft (LRAACA) program, which was to initially replace the existing fleet of 125 Lockheed P-3 Orion aircraft. In October 1988, the Navy selected a derivative of the P-3 Orion (which was later renamed Lockheed P-7A) as the LRAACA aircraft over the P-9D.

On October 10, 1989, McDonnell Douglas publicly announced that it was abandoning the development of propfan-powered aircraft, because of airline companies were concerned about the technology risk and cost compared to a conventionally-powered airliner.