The McDonnell Douglas F-4 Phantom II is an American tandem two-seat, twin-engine, all-weather, long-range supersonic jet interceptor and fighter-bomber originally developed by McDonnell Aircraft for the United States Navy. Proving highly adaptable, it entered service with the Navy in 1961  before it was adopted by the United States Marine Corps and the United States Air Force, and by the mid-1960s it had become a major part of their air arms.