Air Canada Flight 759

On July 7, 2017, an Airbus A320 operating as Air Canada Flight 759 was nearly involved in an accident at San Francisco International Airport in San Mateo County, California, United States. The flight, which originated at Toronto Pearson International Airport, had been cleared by air traffic control to land on runway 28R and was on final approach to land on that runway; however, instead of lining up with the runway, the aircraft had lined up with the parallel taxiway, on which four fully loaded and fuelled passenger airplanes were stopped awaiting takeoff clearance. The flight crew initiated a go-around prior to landing, after which it landed on 28R without further incident. The aircraft on the taxiway departed for their intended destinations without further incident. The subsequent investigation by the National Transportation Safety Board (NTSB) determined that the Air Canada airplane descended to 59 ft above the ground before it began its climb, and that it missed colliding with one of the aircraft on the taxiway by 14 ft.

The NTSB determined the probable cause was the Air Canada flight crew's confusion of the runway with the parallel taxiway, with contributing causes including the crew's failure to use the instrument landing system (ILS), as well as pilot fatigue. A retired pilot stated the runway confusion that almost happened "probably came close to the greatest aviation disaster in history" as five airplanes and potentially over 1,000 passengers were at imminent risk of a disaster greater than the Tenerife airport disaster.

Incident

At 11:46 p.m. local time, Air Canada Flight 759 (AC 759), carrying 135 passengers and 5 crew members, was cleared to land on Runway 28R. The adjacent Runway 28L had been closed at 10 p.m. local time and its lights were off, except for a 20.5 ft lighted flashing "X" at the eastern runway threshold. The captain was flying the aircraft and the first officer was monitoring. The two pilots of AC 759 acknowledged that they mistook runway 28R for 28L and therefore lined up for landing on the parallel taxiway C, even though runways and taxiways are lit with different colours and intensities. Preliminary post-event investigation results noted that Runway 28R and Taxiway C were lit on default settings (in different colours), and the automatic terminal information service broadcast information was current and advised that 28L was closed and unlit. According to preliminary Transportation Board investigation results, as the weather was clear, the pilots of AC 759 were not required to utilize the instrument landing system and relied instead on a visual approach, as typical for the prevailing conditions.

On Taxiway C, four airplanes were queueing for takeoff, three from United Airlines and one from Philippine Airlines. At 11:55:46 p.m. local time, upon spotting aircraft lights approximately 0.7 mi from the runway, the pilot of AC 759 asked the tower if he was clear to land on 28R, to which the air traffic controller responded at 11:55:56 p.m., "There's no one on 28R but you," when AC 759 was approximately 0.3 mi from the runway threshold. The AC 759 pilots "did not recall seeing aircraft on Taxiway C, but something did not look right to them", according to a post-incident interview summary. The pilot of United Airlines Flight 1 (UA 001), the first in line for takeoff, interrupted the radio traffic at 11:56:01 p.m. and asked "Where is this guy going? He's on the taxiway." The crew of Philippine Airlines Flight 115 (PR 115) turned on their landing lights to alert AC 759 they were lined up on the taxiway. Then the captain of AC 759 initiated a go-around, around the same time as the first officer called for a go-around. The air traffic controller ordered AC 759 to abort the landing at 11:56:10 p.m. After AC 759 acknowledged the go-around, the air traffic controller stated, "It looks like you were lined up for Charlie [Taxiway C] there." AC 759 had already started to climb before the go-around order.

Afterwards, the pilot of UA 001 radioed the tower saying, "Air Canada flew directly over us," and the air traffic controller responded, "Yeah, I saw that, guys." During the first approach, AC 759 flew for 1/4 mi over Taxiway C, descended to an altitude as low as 81 ft and approached as close as 29 ft laterally to the four airplanes waiting on Taxiway C before being ordered to abort the landing. According to the flight data recorder, the pilots advanced the thrust levers when the airplane was 85 ft above the ground. The airplane descended as low as 59 ft, approximately 2.5 seconds after the thrust levers had been advanced. There was less than 10 to 20 ft separation between the bottom of the Air Canada aircraft and the tail of the Philippine Airlines Airbus A340 aircraft, which was the second airplane on the taxiway. Following a reconstruction of events, one pilot not involved in the incident noted that had the crew waited five more seconds before pulling up, it would have collided with the third airplane on the taxiway, which was that of United Airlines Flight 863 (UAL 863).

SFO was the first airport in the United States to install an Airport Surface Surveillance Capability (ASSC) system, which should have alerted the tower of a potential conflict between runway and taxiway movements. AC 759 disappeared from the local controller's ASSC display for twelve seconds, between 11:55:52 and 11:56:04 p.m. local time (from shortly after the AC 759 pilot asked for confirmation that 28R was clear, to the time the UA 001 pilot noted that AC 759 was lined up for Taxiway C), as AC 759 was too far off-course from 28R.

AC 759 completed its go-around and landed without incident after the second approach. A single air traffic controller was monitoring ground and tower frequencies, which would typically be handled by two controllers.