Republic of China Air Force IDF Prototype Encounter 1992

On September 3, 1992, a Republic of China Air Force test pilot flying the new Indigenous Defence Fighter (IDF) prototype over the Taiwan Strait encountered a disc-shaped contact during a training sortie. The IDF's advanced Ching-Kuo AIDC radar system showed the contact performing maneuvers that included instantaneous 90-degree direction changes at 30,000 feet. When the test crew attempted to maintain radar track, the contact demonstrated apparent awareness of the radar emissions and performed evasive maneuvers that defeated the AIDC radar's tracking algorithms. The contact departed at a speed the IDF prototype could not match. The encounter was immediately classified by the ROCAF, and the test program documentation was sealed. The incident came to the attention of Taiwan defense research analysts in the early 2000s through retired ROCAF sources. The timing during the testing of Taiwan's first domestically-developed fighter made the classification particularly sensitive.