Asiana Airlines Flight 204 Runway Incursion Incident (N461WN)

Incident Overview and Aircraft Involved<br><br>Asiana Airlines flight 204 (AAR204), operating a Boeing 747-400, was cleared to land on runway 24L at Los Angeles International Airport (LAX). The aircraft initiated a go-around and overflew Southwest Airlines flight 440 (SWA440), a Boeing 737, which had been cleared into position and hold for takeoff on the same runway. Radar reconstruction confirmed that AAR204 passed over SWA440 at a vertical separation of 200 feet during the go-around maneuver.<br><br>## Timeline and Controller Actions<br><br>The incident occurred immediately after a controller change at the LC2 position. At 2151:21, the outgoing LC2 controller cleared AAR204 to land on runway 24L when the aircraft was 9.3 miles from the runway. Approximately two minutes later, the outgoing controller provided a relief briefing to the incoming controller, explicitly stating that AAR204 was landing on runway 24L. The relief controller acknowledged this information. Upon assuming responsibility, the relief controller's first transmission was to SWA440, instructing the crew to taxi into position and hold on runway 24L. At that time, AAR204 was 1.81 miles from the runway at 700 feet altitude. Twelve seconds later, the relief controller cleared SWA440 for takeoff. Radar data indicated AAR204 was 1.26 miles from the runway and approximately 35 seconds from the landing threshold. Flight data from SWA440 showed the aircraft was on taxiway V approaching runway 24L when the clearance was issued, leaving less than 35 seconds to taxi onto the runway, begin a departure roll, and travel 6,000 feet before AAR204 crossed the threshold—a sequence described as impossible.<br><br>## Crew Observations and Avoidance<br><br>The SWA440 captain stated that he saw the Asiana 747 on final approach but believed it was landing on runway 24R. The Asiana captain observed the Southwest 737 approaching runway 24L but initially believed it would hold short. Upon recognizing the aircraft was entering the runway, the Asiana crew initiated a go-around, estimated to have occurred when the aircraft was passing through 400 feet. The relief controller stated he believed AAR204 was landing on runway 24R despite the briefing, and only became aware of the conflict when the Airport Movement Area Safety System (AMASS) generated an alarm approximately 12 seconds before a potential collision. He subsequently canceled both the takeoff clearance for SWA440 and the landing clearance for AAR204, but AAR204 had already overflown the 737.<br><br>## Contributing Factors<br><br>The investigation identified several contributing factors. The relief briefing was interrupted by routine radio transmissions, which likely exacerbated the difficulty the relief controller had in converting briefing information from short-term to working memory. The controller was briefed on seven aircraft, near the limit of effective short-term memory retention, and was not given sufficient opportunity to rehearse the information. LAX tower controllers noted that visual determination of destination runways is difficult for large aircraft like the 747 due to the tower's location. Although the tower is equipped with Digital Bright Radar Indicator Terminal Equipment (DBRITE) displays, the time-sharing of runway assignment information on the aircraft data tag increased the likelihood that critical information would not be perceived during parallel approaches. The relief controller stated he saw AAR204's radar target but did not specifically recall seeing its data block, which displayed runway assignment and aircraft type for only 5 seconds before switching to altitude and ground speed data for 15 seconds.<br><br>## Staffing and Fatigue<br><br>At the time of the incident, five certified professional controllers and one operations supervisor were working in the tower cab, reduced from the normal ten due to injuries and illness. The absence of a local assist controller eliminated an additional safety net. The investigation also evaluated fatigue, noting the relief controller had only 8 hours off between shifts and reported sleeping 5 to 6 hours the night before, resulting in a slight decrease in cognitive performance on tasks involving working memory and reaction time.