A Southwest Airlines crew caused two successive go-arounds at San Francisco International Airport on May 19, 2017, when the aircraft taxied across Runway 28 Left and Runway 28 Right at an unusually slow pace while United Airlines Flight 277 and Alaska Airlines Flight 553 were simultaneously established on final approach to those same runways. The Southwest crew had received and correctly read back a clearance to cross Runway 28 Left and line up and wait on Runway 28 Right — a standard, well-understood instruction — yet their ground speed across the active runways was inconsistent with the urgency the clearance implied. United 277, reportedly just a few hundred feet above San Francisco Bay, initiated a go-around upon spotting the Southwest aircraft still occupying 28 Left. Alaska 553 followed moments later after observing the same aircraft crossing 28 Right. Both flights circled and landed without further incident. The FAA classified both go-arounds as precautionary and determined appropriate steps had been taken; the NTSB declined to open a formal investigation.
The incident carries significant operational weight for crews who regularly operate at airports with closely spaced parallel runways. SFO's 28 Left and 28 Right are separated by only 750 feet — among the tightest parallel runway configurations at any major U.S. airport — a geometry that historically enabled simultaneous independent parallel approaches but also compresses the margin for error during any surface movement across an active final approach corridor. When a crew accepts a cross-runway, line-up-and-wait clearance under those conditions, the implicit expectation is expeditious compliance. Slow taxi speeds on active runways adjacent to occupied final approach paths compress time available for pilots on approach to identify, assess, and respond to a runway incursion, and similarly compress the window for controllers to issue timely go-around instructions. In this case, multiple systems converged correctly: the flight crews made independent go-around decisions before being formally instructed to do so, the controller issued the directive, and the tower's automated conflict detection system generated an advisory — three overlapping redundancies all triggering simultaneously, which underscores how compressed the margins actually were.
The audio from the incident also highlights a secondary but operationally meaningful issue: radio discipline and phraseology under high-workload conditions. The controller and United 277 stepped on each other's transmissions during a critical phase — a recurring vulnerability in busy terminal environments where multiple aircraft are simultaneously executing missed approaches, being sequenced, and receiving taxi clearances. The video commentary also notes a readback error from United 277, illustrating that go-around workload is sufficient to degrade precise communication even among professional crews. Controllers relying on automated ground conflict advisories as a backup layer are a well-established part of modern airport design, but those systems are not a substitute for crew and controller awareness; they are a final-tier redundancy, and their activation alongside a simultaneous pilot-initiated go-around and controller instruction signals that the situation had already progressed deeper into the hazard envelope than any single safeguard was designed to absorb alone.
For Part 91, 91K, and 135 operators that frequently transit large hub airports, the incident reinforces several standing principles. Accepting a clearance implies the ability to comply with it in a timely manner — particularly any instruction that involves occupying or crossing an active runway. Crews operating slower or heavier aircraft should factor their actual ground maneuverability into their situational awareness before accepting such clearances without qualification, and should not hesitate to advise ATC if compliance will be slow. Southwest's cultural reputation for fast taxi operations makes this particular event doubly instructive: institutional reputation is not a substitute for individual crew judgment, and the culture of any airline does not automatically transfer to every crew on every day. The broader takeaway for working pilots is that runway incursions remain a top-tier safety threat, that close parallel runway environments amplify risk exponentially, and that every cross-runway clearance deserves the same urgency and precision as a takeoff clearance itself.