A large Chinese military drone has conducted regular flights over the South China Sea in recent months while transmitting false transponder signals that made it appear to be other aircraft, including a sanctioned Belarusian cargo plane and a British Typhoon fighter jet.

Military attaches and security analysts scrutinizing the operations say the flights represent a step-change in China¡¯s gray-zone tactics in the contested South China Sea and appear to be testing possible decoy capabilities in the event of a Chinese invasion of Taiwan.

Since August, at least 23 flights have been logged under the call sign YILO4200, a known long-endurance Chinese military drone, but the aircraft transmitted registration numbers of other aircraft, according to analysis of data from flight-tracking website Flightradar24.