YC-14 vs YC-15: How a Failed Competition Led to a Transport Icon

In the mid-1970s, Boeing and McDonnell Douglas competed in the USAF Advanced Medium STOL Transport (AMST) program to build a tactical transport that could land on short, rough forward airstrips.

The two companies chose different approaches: Boeing's YC-14 used 'upper-surface blowing' with its engines mounted high and forward, while McDonnell Douglas's YC-15 employed four engines under the wing for externally blown flaps.

Both prototypes exceeded the specified requirements but were cancelled in 1979 due to shifting Air Force priorities. The mission changed from a medium tactical transport to a bigger aircraft with strategic range.

The McDonnell Douglas YC-15's design, however, laid the groundwork for the C-17 Globemaster III, which was awarded the contract in 1981 and has become one of the most capable and heavily used transports in the world.