> “Northrop designed the T-38, the F-5 was derived from it.”
Actually, Northrop hired an independent consultant to design the T-38. He was Edgar Schmued. You may have heard of him as the designer of the P-51 Mustang and the F-86 Sabre. He also did preliminary design work on the F-100 Supersabre before he left North American. After he left them (over a design dispute with management), he set up an independent design consulting company. The T-38 was one result.
I did not know of the follow on designs of Edgar Schmued thanks....