Aircraft Accident Report
Aeronaves De Mexico, S.A. McDonnell Douglas DC-9-32,
XA-JED and PIPER PA-28-181, N4891F, Cerritos, California
August 31, 1986 
NTSB Number AAR-87/07
NTIS Number PB88-910409
available in  hardcopy

Executive Summary: On August 31, 1986, about 1152 Pacific daylight time, Aeronaves de Mexico, S.A., flight 498, a DC-9-32, Mexican Registration XA-JED, and a Piper PA-28-181, United States registration N4891F, collided over Cerritos, California. Flight 498, a regularly scheduled passenger flight, was on an instrument Flight Rules flight plan from Tijuana, Mexico, to Los Angeles International Airport, California and was under radar control by the Los Angeles terminal radar control facility. The Piper airplane was proceeding from Torrance, California toward Big Bear, California, under Visual Flight Rules, and was not in radio contact with any air traffic control facility when the accident occurred.

The collision occurred inside the Los Angeles Terminal Control Area near 6,560 feet mean sea level. At the time of collision, the sky was clear, and the reported visibility was 14 miles. The air traffic controller providing service to flight 498 did not observe the Piper airplane's radar return on his display and therefore did not provide any traffic advisory to flight 498 concerning the location of the Piper airplane before the collision. Both airplanes fell to the ground within the city limits of Cerritos. Five houses were destroyed and seven other houses were damaged by airplane wreckage and post impact fire. Fifty-eight passengers and six crewmembers on the DC-9 were killed; the pilot and 2 passengers on the Piper were killed; 15 people on the ground were killed and 8 others received minor injuries.

The National Transportation Safety Board determines that the probable cause of the accident was the limitations of the air traffic control system to provide collision protection, through both traffic control procedures and automated redundancy. Factors contributing to the accident were (1) the inadvertent and unauthorized entry of the PA-28 into the Los Angeles Terminal Control Area and (2) the limitations of the " see and avoid" concept to ensure traffic separation under the conditions of the conflict.

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