The F-4 was not a joint project in any way. It was a Navy funded aircraft that was later adopted by the Marines and Air Force.<p>Similarly, the A-12 was also a Navy program, not a joint project. The Air Force considered buying it (had it been funded to completion by the Navy) as a replacement for the F-111, but this consideration was largely superficial, and they had little to no input into it&#x27;s design.