Small Aircraft
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 6
Situational Awareness
ATC Issue All Types; Conflict NMAC
Flight Crew Requested ATC Assistance / Clarification
Airport; Human Factors
Aircraft X checked in approximately 12 miles southeast for landing at 025 feet. Aircraft X was issued to enter left base; east of the wash approximately 2 minutes later Aircraft X reported a near miss with an Aircraft Y. Aircraft X stated the aircraft passed behind about 500 feet lower. A target was observed with no altitude indication passing behind Aircraft X speed indicate 140 knots. Target was not observed prior to the report due to other aircraft in the vicinity of the airport. I should better scan for fast moving aircraft departing adjacent airports.
CNO Tower Controller reported an aircraft entering their pattern reported a NMAC.