F20 Tigershark
YF17 was a prototype for the F18 I think
RTR
It was the YF17, which was also the predecesor to the Navy's F-18. If I recall it was a joint design competition by the Air Force and Navy (and maybe Marines also), in teh end the AF chose the F-16, and the Navy (and Marines) the YF-17 with required modifications - aka the first generation F-18 (folding wings, reinforced landing gear, different midair refueling equipment and basic avionics equipment/support from the AF standards, and the arrestor hook off the top of my head).