The official Request for proposal (RFP) was issued in January 1972, asking for operations into a 2,000-foot (610 m) semi-prepared field with a 27,000-pound (12,000 kg) payload and a 400-nautical-mile (460 mi; 740 km) mission radius.

Proposals were submitted by Bell, Boeing, Fairchild, McDonnell Douglas and the Lockheed/North American Rockwell team at this stage of the competition.

[2] McDonnell Douglas's design incorporated a supercritical wing, the result of NASA research carried out by the already famous Richard Whitcomb.

This wing design dramatically lowers transonic wave drag by as much as 30% compared to more conventional profiles, while at the same time offering excellent low-speed lift.

Most contemporary aircraft used swept wings to lower wave drag, but this led to poor low-speed handling, which made them unsuitable for STOL operations.

Although the effects had been studied for some time at NASA, along with similar concepts, until the introduction of the turbofan the hot and concentrated exhaust of existing engines made the system difficult to use.

[3] For later prototypes, there were several modifications including a computer on the YC-15 was devised that would calculate the best flap angle for various flight conditions given the current gross weight.

It was especially designed to help with short field landings, showing the pilot the horizon, flight path scale, airspeed indexer and touchdown point.

In November 1976, both designs were transferred to Edwards Air Force Base for head-to-head testing, including lifting heavy loads like tanks and artillery from dirt airfields at Graham Ranch, off the end of Runway 22.

Because of slow actuation of the thrust reversers, testing at Edwards AFB showed the plane was unable to consistently stop in “hot-and-high” conditions in the required 2000 feet.

This led to a series of studies that basically stated that such a modification was not easy, and would require major changes to either design to produce a much larger aircraft.

One aircraft (72-1875) was subsequently moved to the nearby Pima Air & Space Museum in 1981,[17] but was returned to flying status by McDonnell Douglas in 1996; it was first reflown on 11 April 1997.