In the early 1970s, the single-seat F-5E was developed as a follow-on to the F-5A. The F-5E incorporated higher thrust engines, a larger wing, and greater internal fuel capacity. The F-5E also was given a more advanced weapon delivery system than the F-5A, incorporating, for the first time, a search radar. The prototype F-5E made its first flight in 1973. A dual-seat version was also developed (the F-5F) and made its first flight in 1974.
The F-5E/F aircraft were sold to 23 different countries. The USAF and USN operated the aircraft as surrogate threat aircraft in the famous Aggressor and Top Gun programs. A total of 1183 single-seat F-5Es and 241 dual-seat F-5F aircraft were built. More than 900 F-5E/F aircraft are still in operational service in 22 countries.
Programs to upgrade the avionics systems in the F-5E/F and extend the structural life of the airframe have been undertaken in many countries, including Chile, Brazil, Thailand, Jordan, Singapore, Indonesia and Morrocco.