A system for graphically displaying on a cockpit display an indication of
closure (i.e. a "closure indictor") with a selected target aircraft. In a
preferred embodiment of the invention, the system only displays a closure
indicator if: (1) the selected target aircraft is within a pre-determined
monitoring zone; and (2) the track of the selected target aircraft is
within a pre-determined variation angle of the track of the Own Ship
aircraft. If the rate of closure between the selected target aircraft and
the Own Ship aircraft is within a predetermined range of values, the
closure indicator includes a closing/receding indicia (such as an
upwardly or downwardly directed arrow) that indicates whether the Own
Ship aircraft is closing in on or receding from the selected target
aircraft. The system preferably removes the closure indicator from
display when the Own Ship aircraft or the selected target aircraft ceases
to be airborne.