What happened
On the morning of the accident, an AeroMéxico flight, operating as AM498, was performing a scheduled service from Tijuana to Los Angeles with several intermediate stops. The aircraft, a DC-9 known as 'Hermosillo', departed Tijuana Airport at 11:20 and was cruising at 10,000 feet. During the flight, Coast Approach Control instructed the crew to descend to 7,000 feet.
Simultaneously, a Piper PA-28-181 Cherokee, registration N4891F, departed Torrance Airport for a visual flight rules trip to Big Bear. The aircraft carried a pilot and two passengers. While navigating toward the Paradise VORTAC, the Piper entered the Los Angeles Terminal Control Area without obtaining the necessary air traffic control clearance.
At 11:47, the AeroMéxico crew reported being level at 7,000 feet to LA Approach Control. The controller subsequently provided instructions for a heading of 320 degrees and an eventual descent to 6,000 feet with a reduced airspeed of 190 knots. At approximately 11:52:09, the DC-9 and the Piper collided at an altitude of roughly 6,560 feet over Cerritos. The impact occurred when the Piper struck the left side of the DC-9's vertical and horizontal stabilizer. This contact caused the stabilizer to separate from the tailplane and sliced through the cabin of the Piper. Both aircraft fell out of control following the collision. The resulting wreckage and subsequent fires caused significant damage to several residences, leading to 15 fatalities among those on the ground.
Findings
Investigations into the accident highlighted that the primary contributing factor was the unauthorized entry of the Piper into the controlled terminal area. Additionally, investigators noted the inherent limitations of the 'see and avoid' principle for maintaining separation in such conflicts. The incident also pointed to deficiencies in the air traffic control system regarding its ability to provide collision protection through automated redundancy and established procedures.