KF-21's Accident-Free Test Flights: A Miracle
[Manmoolsang] South Korea's domestically developed fighter achieves 1,600 accident-free test flights in three and a half years, a rare milestone in global fighter development
By Ahn Yong-hyun
Published 2026.01.13. 19:55Updated 2026.01.14. 13:33
Fighter development hinges on test flights. Typically conducted around 2,000 times, these flights are fraught with failures and accidents. The U.S. began developing the F-111, a multirole fighter for the Navy and Air Force, in the 1960s. It was designed with technologies like variable-sweep wings (adjustable wing angles). However, the Navy clashed with the Air Force, arguing that the fuselage needed to be shorter to fit on aircraft carriers. The defense secretary at the time ordered a design halfway between the lengths requested by the Navy and Air Force. During test flights, it repeatedly crashed and even disintegrated mid-air. Ultimately, only the Air Force adopted it, while the Navy separately developed the F-14 fighter featured in the movie “Top Gun.”
▶The U.S. developed the high-speed interceptor F-104 and deployed it to allied nations. It completed test flights in the U.S. However, Europe’s terrain and climate differed from America’s. In West Germany alone, over 270 aircraft crashed, killing over 100 pilots. It earned nicknames like “widowmaker” and “flying coffin.” The U.S. stealth fighter F-35 underwent over 9,200 test flights for 10 years. Integrating advanced software into the airframe proved challenging. Errors occurred during each test flight, requiring fixes. India conducted test flights for its domestically developed light fighter for nearly 20 years, yet it remains unstable, crashing recently.
▶The commander of the ROK Air Force test flight squadron stated, “Test flights for newly developed fighters involve pushing uncompleted airframes into uncharted operational territories.” This means deliberately setting risks and limits and flying into them. Fighters must endure rapid climbs, sudden accelerations, high-speed turns, and more. Accidents can occur even during missile launches. Nowadays, complex software poses issues. Systems function normally on the ground but malfunction in the air. The prototype of the top-tier F-22 once crashed after the pilot fainted. Countless pilots have died in test flights. China and Russia conceal their test flight accidents.
▶Test flights are a process where nations test the limits of newly developed fighters at the risk of pilots’ lives. Only the best pilots can conduct them. The F-16 test pilot became the U.S. Air Force Chief of Staff. Major countries assign test flight veterans to air force command positions, recognizing their comprehensive capabilities in extreme situational judgment and technical understanding.
▶Yesterday, South Korea’s domestically developed supersonic fighter KF-21 finally completed its test flights. It underwent over 1,600 accident-free test flights in three and a half years. In fighter development, it is rare to find a case like the KF-21, which completed test flights in such a short period without any casualties. The KF-21 test pilot said, “To put it crassly, I feel a sense of ‘national pride.’” Many citizens likely share this sentiment.
KF-21s Accident-Free Test Flights: A Miracle Manmoolsang South Koreas domestically developed fighter achieves 1,600 accident-free test flights in three and a half years, a rare milestone in global fighter development
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