McDonnell F-4D

As is now well-known, development of the Phantom II— the outstanding U.S. fighter and reconnaissance aircraft of the sixties and early seventies—was undertaken more than 30 years ago when the McDonnell Aircraft Company initiated configuration studies in August 1953 calling for an all-weather attack fighter intended as a follow-on for its F3H Demon. The base versions, which were assigned the McDonnell Model No. 98 and the series letters A and B respectively, were single-seat aircraft with 45 degree sweptback wings, a gross wing area of 450 sq ft., four 20mm cannon and external stores. The Model 98-A was to have been powered by a single Wright J67-W-1 turbo­jet and the Model 98-B was to have had two General Elec­tric J79-GE-2 turbojets.
The Navy's Bureau of Aeronautics, however, prefer­red to sponsor the development of a two-seat fighter, and it was the Model 98-R which was ordered in September 1955 as the XF4H-1. More studies followed this signifi­cant Phantom II event and, after exhausting the single series letters (although the letters G, H. I, J. and 0 were not used), McDonnell began assigning dual series letter designators.