SkyWest Airlines Flight 5086

The runway incursion occurred when a CRJ inadvertently turned onto a highspeed exit taxiway and entered a runway after a Boeing 737 was cleared for takeoff on the same runway. Air traffic control ground controller issued the pilots of the CRJ taxi instructions to runway 28L from their ramp exit point. The instructions included clearance to cross runway 1 left and runway 1 right. Subsequently, the ground controller issued revised taxi instructions requiring the pilots to taxi on the taxiway closest to but parallel to runway 28L, then make a slight right turn to another taxiway to taxi to the approach end of runway 28L. During the taxi, the captain made a left turn onto a runway 28L highspeed exit and began to cross the runway hold short line, instead of making the slight right turn required to follow their taxi clearance. The captain reported that "something did not feel right" and stopped the airplane as the ground controller commanded the CRJ to stop. Although the captain of the CRJ had taxied at San Francisco International Airport (SFO) "many times" and was familiar with a hotspot in the area he made the mistaken turn, he had no explanation as to why he turned left at that point in the taxi. Recorded data indicated that the B737 passed in front of the CRJ within 188 feet laterally. The pilots of the B737 did not observe the CRJ during the takeoff roll. A review of air traffic control procedures and equipment showed that appropriate procedures were followed and there were no irregularities noted with the equipment. Federal Aviation Administration guidance on taxiway design indicated that complex intersections increase the possibility of pilot error. It offered the "three-node concept" which means that a pilot is presented with no more than three choices at an intersection. The intersection where the incursion began contained five choices: a left turn, a slight left turn, straight, slight right turn, and a right turn. After this incident, SFO placed temporary barricades at this intersection preventing its use before permanently closing the taxiway. Following this event, SkyWest Airlines developed and disseminated, on January 19, 2017, a "Flight Operations Message" to all pilots titled "Surface Movement Safety – Preventing Incursions" discussing the events surrounding this event and what crews should do to be vigilant.

Although the area in which this incident occurred may have contributed to the captain’s mistaken turn, it was designated as a hot spot location that required enhanced crew vigilance during wayfinding through this area. Further, there were multiple cues at the intersection before the turn was made that could be used by the pilots to support the wayfinding task. Finally, the taxiway in which the captain mistakenly turned had signs, marking, and lighting to indicate both the identification of the taxiway and the identification of and presence of a runway and the fact it was active. These cues were not heeded by either pilot before the airplane entered the runway.

Verbatim NTSB analysis and probable cause from the NTSB dataset