Voice recognition
Back in the 60’s a RAF pilot used to fly from Singapore to Hong Kong on a regular basis.. He was a regular so his voice was well known. In the 70’s, after a 10 year break, he returned to Changi and started flying the route again. On his first trip he radioed Hong Kong from a distance and was surprised to hear a voice saying “Captain Clark, welcome back to the Far East”. On landing at Kai Tak he went to the control tower to find the ATCO who had recognised his voice. They denied all knowledge of his call. It was probably the Chinese listener who was monitoring all inbounds to Kai Tak and who could not resist the welcome message as he recognised Capt Clark’s voice.