The accident investigation revealed no single cause but a cascade of them. The airport's ground surveillance radar system was not functioning that evening, leaving controllers without the visual confirmation they normally relied on. Wascher, working alone in the tower, had failed to issue USAir 1493 a 'position and hold' clearance before the SkyWest plane entered the runway — the standard sequence that would have prevented the conflict. And when investigators examined the cockpit of the USAir aircraft, they discovered that Captain Colin Shaw had measurable levels of phenobarbital in his blood, suggesting he was taking medication that may have affected his alertness. Shaw died in the crash.

The impact ignited a fire that began in the Boeing's forward cargo hold and spread rapidly through the passenger cabin. In the darkness and smoke, survivors scrambled for exits that were blocked or inaccessible. Sixty-six people made it out alive from the USAir aircraft; twenty-three did not. The SkyWest Metroliner, crushed beneath the impact, offered no survivors. Among those who walked away from the burning 737 was David H. Koch, the billionaire industrialist, who had been seated toward the rear of the plane. The randomness of survival — determined largely by where each passenger happened to sit — haunted the aftermath of the accident.

The National Transportation Safety Board investigation led to significant changes at Los Angeles International Airport. The FAA required LAX to reorganize its runway use patterns to reduce the likelihood of similar conflicts. A new control tower was commissioned to give controllers better sight lines and modernized equipment. Ground radar systems, which had been allowed to fall out of service, were repaired and maintained more rigorously. The accident also contributed to broader changes in how controllers manage multiple aircraft on active runways during low-visibility conditions — lessons that would prove relevant at airports across the country in the years that followed.

Runway incursions — the technical term for unauthorized or unexpected presence on an active runway — happen more often than most passengers realize. LAX handles hundreds of takeoffs and landings every day, and the geometry of a busy airport means aircraft are constantly crossing active runways, holding on taxiways, and queuing in complex patterns that controllers must track simultaneously. The 1991 collision occurred in part because those systems had gaps: gaps in technology, in procedure, and in the human attention required to catch errors before they became catastrophes. The memorial to the 35 who died is the safety infrastructure that now exists because they did.