Oops, the F-18 was a development of the Northrup YF-17 (that was developed from the F-20, that was developed from the F-5) that was in competition with the F-16, MD only got it after buying Northrup. Not trying to snark here, that's just what happened.
I wondered how much the YF-17 (first flew in 1974) could have derived from the F-20 (first flew in 1982). According to Wikipedia, the YF-17 came from a third-generation concept deriving from the F-5E, said lineage beginning in 1965. So both the YF-17 and the F-20 derived from the F-5E, although along different developmental paths.
The F/A-18, while visually similar to the YF-17, was very different structurally because of the requirements for a carrier-suitable Navy aircraft.
McDonnell Douglas never bought Northrop: MD and Northrop teamed in the Navy competition that produced the F/A-18. MD was brought in because of their creds producing naval jets, and ended up as primary contractor on the naval variant; as part of the agreement, Northrop was to be prime on any export land-based variants (the F-18L, which never really materialized). Later, Northrop merged with Grumman and MD was purchased by Boeing.
All that aside, I'm personally quite fond of the F-5/T-38 series (the T-38 was an aerodynamicist's dream) and would welcome several repaints into my 1/18 hangar. While it didn't have a front-line U.S. military presence, it served as the USAF advanced trainer, flight demonstration and NASA research aircraft, and, as others have said, has served in many small (and sometimes colorful) air forces around the world, including the VNAF.
If there was only to be one more 1/18 aircraft ever produced (gad!), I wouldn't have chosen the F-5/T-38, but I'll support it if it comes along with the others.
aae83