 In September the defection of a MiG-15 pilot (with his aircraft) enabled US pilots to assess their erstwhile opponent at first hand.The MiG that Lieutenant No Kum-sok flew into Kimpo on September 21 was one of the later MiG-15SDs.According to Budiansky, "In late March 1951, the 1st RSM (1st Radio Squadron, Mobile), still operating in Japan, picked up Russian ground controllers in voice communication with Soviet MiG fighter aircraft operating over North Korea.