In 1972 the Air Force's Prototype Program Office at Wright-Patterson AFB, Ohio, launched the Lightweight Fighter (LWF) program, and the request for proposals (RFP) called for a highly maneuverable fighter with a significant emphasis on reduced weight but also cost. The program wasn't originally intended to lead to a production aircraft, but rather to determine what was possible at what cost. While five contractors competed for the LWF two finalists emerged – General Dynamics and Northrop, which would build two prototypes of their respective designs, the YF-16 and YF-17. As the program continued four European members of NATO – Belgium, Denmark, the Netherlands, and Norway – sought to replace the F-105Gs with a lighter and more affordable fighter.