Abstract: An aircraft proximity monitoring method according to the invention comprises the steps of: continuously and repeatedly developing and transmitting signals corresponding to the positions relative to a first location of aircraft within a predetermined range of said first location receiving said transmitted signals at a given aircraft and transposing the signals corresponding to the positions of the others of said aircraft to said second signals corresponding to the positions of said other aircraft relative to the location of said given aircraft and producing an observable indication of the positions of said other aircraft relative to said location of said given aircraft. Apparatus according to the invention includes apparatus for performing each of the foregoing steps.