This was Boeing's entrant into the USAF's Advanced Medium STOL Transport (AMST) competition that aimed to replace the C-130 Hercules as the USAF's tactical transport aircraft. Although all specifications were met this plane never made it into production and the USAF eventually decided to go with an updated C-130 and a larger transport (hence the C-17). This one still has traces of its former civil registration N8740 visible on the tail. Registered as such to Boeing on 12 Oct 1978, cancelled 1 Apr 1980.

This was the second prototype of an experimental STOL transport aircraft designed for the USAF, seen here at the Paris Airshow.