The approach favors agility over raw power in dealing with human opponents in any endeavor. Boyd put the ethos into practice with his work for the United States Air Force. He was an advocate of maneuverable fighter aircraft, in contrast to the heavy, powerful jet fighters (such as the McDonnell Douglas F-4 Phantom II) that were prevalent in the 1960s. Boyd inspired the Lightweight Fighter program (LWF) that produced the successful General Dynamics F-16 Fighting Falcon and McDonnell Douglas F/A-18 Hornet, which are still in use by the United States and several other military powers into the 21st century.