Abstract: The system provides each equipped given aircraft with an indication of the presence of a similarly equipped intruder aircraft. Various zones are established about the given and intruder crafts and the indication provided tells each pilot when two of these zones overlap. The zones are established by positioning a plurality of transmit/receive antennae about the body of each craft. The dispersion angle and range of each antenna defines a separate one of the zones. Each antenna transmits a signal coded to indicate the location of its zone upon its respective aircraft, and is equipped to receive similarly coded signals transmitted by the other aircraft. These signals are decoded to give an indication of the zone of the intruder aircraft nearest the zone defined by the receiving antenna of the given aircraft. This information is displayed on a cockpit mounted display panel to provide an imminent collision warning which also shows the relative positions of the two aircraft.