​On February 1, 1991, at 1807 Pacific standard time, USAir flight 1493, N388US, A Boeing 737-300 collided with skywest flight 4459, N683AV, a Fairchild Metroliner (SA-227-AC), while the USAir airplne landing on runway 24 left at Los Angeles International Airport, Los Angeles, California. The Skywest Metroliner was positioned on the same runway at intersection 45, awiating clearance for takeoff. As a result of the collisio, both airplanes were destroyed. All 10 passengers and 2 crewmakers aboard the Metroliner and 20 passengers and 2 crewmembers aboard the USAir airplane were fatally injured. 

​​We determined that the probable cause of the accident was the failure of the Los Angeles Air Traffic Facility Management to implement procedures that provided redundancy comparable to the requirements contained in the National Operational Position Standards and the failure of the FAA Air Traffic Services to provide adequate policy direction and oversight to its air traffic control facility managers.  These failures created an environment in the Los Angeles Air Traffic Control tower that ultimately led to the failure of the local controller 2 (LC2) to maintain an awareness of the traffic situation, culminating in the inappropriate clearances and subsequent collision of the USAir and Skywest aircraft.  Contributing to the cause of the accident was the falure of the FAA to provide effective quality assurance of the ATC system.

​​​As a result of the investigation, we issued recommendations to the Federal Aviation Administration.