FlightFollowerSouthwest Lands While SkyWest Still on SAME Runway
At 17:45 on 10 June 2021, San Diego International Airport's Runway 27 was occupied by a SkyWest Embraer while a Southwest Boeing 737 was approaching to land. The tower controller had instructed SkyWest to line up and wait, but the surface detection system later issued a mandatory runway-conflict alert. The controller transmitted a go-around instruction to Southwest, yet the NTSB found that the transmission was blocked and the Southwest crew did not hear it. The 737 maneuvered around the Embraer and landed. The aircraft came within 0.18 nautical mile laterally and 200 feet vertically.
Accident Facts
- Date
- 10 June 2021
The instruction existed, but the crew did not receive it
The key finding is not that the controller failed to issue a go-around. The controller did issue it. The problem was that the transmission was blocked. The NTSB reviewed FAA recordings and found that simultaneous transmissions likely canceled each other without an indication to the controller or the aircraft.
The Southwest crew therefore continued the approach. When the crew became aware that an aircraft was on the runway, the first officer maneuvered the 737 left and then back right to avoid overflying the SkyWest aircraft. The Boeing landed after the Embraer moved clear.
Distraction became part of the chain
The NTSB found that the controller had also been communicating with a helicopter transitioning the airspace after instructing SkyWest to line up and wait. The investigation concluded that this additional communication likely distracted the controller from monitoring the positions of the two aircraft.
The report also noted that the FAA had been asked to test radio-signal strength but there was no indication that the testing was completed. The NTSB therefore could not conclusively determine whether signal strength played a role, but considered simultaneous transmissions the likely reason the go-around was blocked.
The documented finding
“The blocked go-around radio instruction from the air traffic control tower to the arrival aircraft which resulted in the arrival aircraft continuing the landing approach.” — National Transportation Safety Board, OPS21LA003
Conclusion
The San Diego event was a runway-incursion chain built from several ordinary actions that became incompatible: a landing clearance, a line-up-and-wait instruction, an instruction to vacate, a surface alert and a go-around call. The critical protection failed at the communications interface. The controller believed the go-around had been transmitted; the arriving crew did not hear it. The NTSB's finding therefore focused on the blocked transmission and the controller's distraction rather than treating the event as a simple pilot failure to comply.