A US Air Force (USAF) plane changed its aircraft identification code as it flew over the Yellow Sea on Tuesday – making it appear like a Philippine aircraft, according to the Beijing-based South China Sea Strategic Situation Probing Initiative (SCSPI). Dr Collin Koh, a Research Fellow at the RSIS, said that even with the growing military tension between China and the United States, in peacetime, a country would not use its air defences against an aircraft until its identity had been clearly confirmed. “There are clear restrictions on the type of action air defences can take against suspicious aerial activity,” he said.