YC‑15 Innovations and AMST Program Termination

McDonnell Douglas responded to a 1960s Air Force request for an Advanced Medium STOL Transport (AMST). The prototype, designated YC‑15, first flew on 26 August 1975. It pioneered two key technologies: externally blown flaps, which use the aircraft’s own jet exhaust to augment lift at low speeds, and a system that channels exhaust over the wing to further increase lift during short takeoffs and landings. (Primary source)

The Air Force ultimately rejected the YC‑15 and terminated the AMST program. The decision was based on a strategic shift toward a larger, more capable airlifter. Although the YC‑15 never entered production, its design elements informed the later C‑X program and eventually the C‑17 Globemaster III, which won the 1981 contract and entered service in 1995. (Primary source)