OP does not clarify if the military jet was tactical or transport, nor its vintage. Current production tactical intercept aircraft would likely be equipped with one a family of all-weather multimode radar systems designed for air superiority fighters. These X band pulse-Doppler radar systems are designed for both air-air and air-ground missions; they are able to look up at high-flying targets and down at low-flying targets without being confused by ground clutter. The systems can detect and track aircraft and small high-speed targets at distances beyond visual range down to close range, and at altitudes down to treetop level. The radar feeds target information into the aircraft's central computer for effective weapons delivery. For close-in dogfights, the radar automatically acquires enemy aircraft and projects this information onto the cockpit head-up display. If this was a transport category a/c it may be equipped with a version of TCAS that provides resolution advisories in responce to interrogations of the intruder VFR aircraft's Mode C equipped transponder.