Investigation Summary
The incident occurred under visual meteorological conditions during a period of intersecting runway operations. SkyWest 5741 (operating as United Express) was cleared to land on runway 28R. Simultaneously, Republic 4912 (operating as Frontier) was cleared for takeoff on runway 1L. The local controller failed to ensure adequate separation between the two aircraft. The Airport Movement Area Safety System (AMASS), which had recently been updated to detect conflicts on intersecting runways, triggered an aural alert at 1335:40. The controller, while mid-transmission with another aircraft, heard the alert and subsequently instructed the SkyWest crew to 'hold, hold, hold.' The SkyWest aircraft came to a stop directly in the intersection. The Republic crew, already at high speed, elected to continue the takeoff and overflew the stationary turboprop. Estimates of the miss distance varied significantly: the FAA initially estimated 300 feet, the Republic crew guessed 150 feet, and the SkyWest crew estimated they were missed by only 30 to 50 feet. Investigation revealed the AMASS clock was approximately 15 to 16 seconds fast; consequently, all official report times were synchronized to the authoritative Automated Radar Terminal System (ARTS) clock.
Final Conclusions
The National Transportation Safety Board determined the probable cause was the failure of the SFO tower local controller to provide adequate separation between two aircraft departing and landing on intersecting runways. The controller was decertified following the incident, underwent remedial training, and was later recertified. The AMASS system was noted to have performed exactly as designed, providing the required 15-second advance warning that prevented a ground collision.
Photographic Evidence (1)
Video Analysis
Runway Incursion Republic Airlines E170 and SkyWest E120 — Animated reconstruction of the 2007 San Francisco runway incursion involving an Embraer 170 and an Embraer 120.
If playback is blocked, the owner has disabled embedding — use the link above.
Systems & Failure Modes
AMASS
Airport Movement Area Safety System; a ground radar system providing conflict detection alerts to controllers. It provided a 15-second warning in this incident.
ASR-9
Terminal radar system located at Oakland International Airport used to track the aircraft during the approach and initial climb phases.
Interesting Facts
- 01The intersection was approximately 1,860 meters from the landing threshold and 1,580 meters from the takeoff threshold.
- 02The AMASS software had been updated just three months prior to detect intersecting runway conflicts.
- 03The local controller involved had been fully certified at SFO since 1999.
- 04Republic 4912 was using the radio callsign 'Brickyard 4912'.
- 05Vertical separation at the moment of conflict was estimated to be as low as 30 feet by the SkyWest crew.
- 06The NTSB report contains conflicting registration data for the Embraer 170, listing both N872RW and N757AT.
Safety Actions & Advisories
Controller Remediation
The involved local controller was decertified, required to complete additional training, and subsequently recertified by SFO tower management.