[yarddog]

I think this plane actually began life as the F-5 Freedom Fighter. Also a trainer.

It has just kept on evolving.

[SJSAMPLE]

No.
Completely different design than the Northrop F-5.
The F-18 began as the YF-17 that competed against the YF-16 for the USAF lightweight fighter competition. It was a completely new design, but lost to the YF-16, which became the F-16.

The YF-17 was brought back as the F/A-18 for the Navy, Marines and export customers.

[paddles]

Northrop P-530 then YF-17.

[DesertRhino]

Neg, it started as the YF-17

[pfflier]

No, The Hornet started as a "clean slate design" competitor for the USAF's light weight fighter program in the 1970s. It was designed by Northrop and was given the designator F-17. It lost that competition to the F-16.

The program was resurrected by McDonnell Douglas and presented to the US Navy as a replacement for fleet fighters and attack airplanes. That us how it got the designator F/A-18. Boeing acquired McDonnell Douglas and is now the manufacturer by title, but not concept or design.

[PJammers]

The F-5 evolved from the T-38. The F-20 Tigershark was the next generation. The F-16 was chosen by the USAF instead. Only 3 were ever produced.

Iran actually developed and currently flies a newer version.