The Republic of China Air Force retired its last F-5E/F Tiger II third generation fighter aircraft in July 2025, marking the end of over 60 years of F-5 operations by a service which previously fielded the type in greater numbers than any other. While the Republic of China’s lack of international recognition prevented it from procuring fourth generation fighters during the Cold War, enhanced F-5E/F variants of the original F-5 were procured in the 1970s, with over 300 being produced under license at a time when other American security partners were transitioning to the more advanced F-16 and F-18. With he F-5 already considered effectively obsolete by the 1970s, the ageing of these aircraft led the Air Force to consider options to significantly improve the fleet’s combat potential through enhancements using indigenous technologies.
The modernisation of lightweight pre-Vietnam War era fighters would hardly have been unprecedented, with the Indian Air Force having enhanced its license MiG-21 fighters, which were broadly considered Soviet equivalents to the F-5, with fourth generation technologies, including radar and infrared guided air-to-air missiles and electronic warfare systems that far surpassed those of early production F-16s. The Republic of China Air Force similarly planned to update its F-5E/F fighters with locally developed fourth generation radars and electronic warfare systems and a MIL-STD-1553B data link, improving situational awareness and survivability. The fighters were also to be equipped with the indigenous the Sky Sword II developed for the local F-CK Ching Kuo fourth generation fighter, providing an advanced beyond visual range radar guided air-to-air capability.
The Sky Sword II’s 100 kilometre engagement range and active radar guidance capabilities placed it broadly on par with the American AIM-120C and mainland Chinese PL-12. Developed by the National Chung-Shan Institute of Science and Technology, and while revolutionising the capabilities of the Ching Kuo fleet, would have provided a tremendous improvement for the F-5. The Sky Sword II’s electronic warfare countermeasures are considered state of the art, and it makes use of an inertial navigation system with a data link for mid course guidance and active radar homing for terminal guidance. According to Su Tzu-yun, Chief Executive Officer at the Center for Advanced Technology at Tamkang University, the missile’s entry into service had the potential to offset mainland Chinese air superiority, at a time when the two rival Chinese governments remained officially in a state of civil war.
Ultimately despite its versatility and very low sustainment costs, the F-5’s very short range and small radar size limited its combat potential even if modernised, which made investments in enhancing the aircraft appear to be far from cost effective. While the F-5 was competitive during the Cold War, when mainland China fielded only locally enhanced derivatives of Soviet fighters from the 1950s, the rapid modernisation of mainland aerial warfare capabilities from the early 1990s made the old American aircraft far from viable. The rapid shift in the balance of power across the Taiwan Strait has culminated in the Chinese mainland today fielding a very high performing fifth generation fighter fleet, that is rivalled only by that of the U.S. Air Force, while the country is poised to begin to operationalise sixth generation fighters in the early 2030s leaving the Republic of China Air Force close to two full generations behind.