[1] The Boeing engineers were aware that NASA had carried out a series of "powered lift" studies some time earlier, including both externally blown flaps, as well as upper-surface blowing (USB), an unusual variation.

Boeing immediately started to build wind-tunnel models to verify the NASA data with layouts more closely matching their own designs.

Additionally, the design has a larger leading edge radius that makes it particularly suitable for low-speed high-lift applications like a transport.

The request for proposal (RFP) was issued in January 1972, asking for operations into a 2,000-foot (610 m) semi-prepared field at 500 nautical miles (930 km) with a 27,000 lb (12,000 kg) payload in both directions with no refueling.

Joe Johnson and Dudley Hammond both reported on testing and showed Wimpress data that verified the high-lift performance that Boeing had quoted in its proposal.

Langley was particularly interested in the effectiveness of the D-shaped nozzle that directed the jet flow over the upper surface of the wing, as well as the resulting sound levels, at that time a major focus of NASA's civilian aerodynamics research.

The first was a problem with air circulating around the wing when operating at low speeds close to the ground, which had a serious effect on the spreading of the jet flow through the nozzle.

In response, Boeing added a series of vortex generators on the upper surface of the wing, which retracted when the flap was raised above 30°.

This positioning turned out to interfere with the airflow over the wings during USB operations, and a new tail with a more vertical profile was introduced to move the elevator forward.

In March 1976, the Air Force Chief of Staff, Gen. David C. Jones, asked the Air Force Systems Command to see if it would be possible to use a single model of the AMST for both strategic and tactical airlift roles, or alternatively, if it would be possible to develop conventional derivatives of the AMST for the strategic airlift role.

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.