The SkyWest aircraft was arriving at SFO after a flight from Modesto, California, and was cleared to land on runway 28R. At the same time, the Republic Airlines aircraft, bound for Los Angeles, California was instructed to taxi into position and hold on the intersecting runway 1L. As the landing SkyWest aircraft passed the runway threshold the Republic Airlines aircraft was cleared for takeoff. Local procedures and FAA Order 7110.65 require the local controller to wait until the landing aircraft has passed through the intersection before clearing an aircraft for takeoff on one of the intersecting runways. Approximately 27 seconds later the Airport Movement Area Safety System issued an aural warning of an imminent collision, and the local controller instructed the SkyWest aircraft to stop, transmitting, "uh, sky-, skywest uhh fifty seven forty one HOLD HOLD HOLD". The SkyWest aircraft came to a stop in the intersection of runways 1L and 28R, while Republic Airlines flight lifted off and overflew it. The initial FAA tower report estimated the aircraft missed colliding by ; while the SkyWest crew estimated the distance as to.
Investigation
The FAA categorized the incident's severity as "Category A", the most severe; Category A is defined as when "separation decreases and participants take extreme action to narrowly avoid a collision, or the event results in a collision." Of the previous 15 runway incursions at SFO between 2001 and 2007, none of them were more serious than Category C, defined as the situation where "separation decreases but there is ample time and distance to avoid a potential collision". Commenting on the seriousness of the incident, NTSB spokesman Ted Lopatkiewicz noted that "We investigate probably just a handful a year." The NTSB's investigation was completed in November 2007, finding that the controller had failed to provide adequate separation between the two aircraft. FAA spokesman Ian Gregor said "This wasn't a procedural issue, this was caused by a good controller with a lot of experience making a mistake", adding that since the incursion the controller had to be recertified for their job. The controller had over 20 years of experience.
SFO and AMASS
Runway safety has been a priority concern for both the FAA and NTSB; it has been on the NTSB's annual list of "Most Wanted Improvements" continuously since 1990. Airport Movement Area Safety System is an airport surveillance radar system that is designed to detect potential runway conflicts and alert controllers. SFO was selected by the FAA for the first test installation of the AMASS system, where it became operational in June 2001, before being rolled out to 40 airports around the United States. In a scenario such as this conflict, AMASS is designed to provide an alert 15 seconds before the aircraft reach the conflict point, and the system performed as designed. However, the NTSB has noted that while AMASS alerted in this incident, it did not alert in time to prevent the runway incursion. , the NTSB continues to list the 2007 SFO runway incursion as evidence that AMASS is insufficient to prevent runway incursions, and as a result, to list a requirement for positive ground movement control on the board's "Most Wanted Transportation Safety Improvements" list.
