The National Transportation Safety Board (NTSB) said that an Air Canada flight crew’s "lack of awareness" caused a July 7, 2017, overflight of a taxiway at San Francisco International Airport.

In the incident, Air Canada flight 759 was cleared to land on runway 28R. Instead, the crew lined up with parallel taxiway C where four airplanes were awaiting clearance to take off.

The Air Canada flight descended to an altitude of 100 feet and flew over the first of the four airplanes. The flight crew started a go-around, and flight 759 was as low as 60 feet above ground level and overflew a second airplane before it started to climb.

As a result of its investigation, the NTSB issued six safety recommendations to the Federal Aviation Administration and one to Transport Canada. The recommendations include the need for airplanes landing at primary airports within class B and class C airspace to be equipped with a system that alerts pilots when an airplane is not aligned with a runway.

The NTSB also called for more effective presentation of flight operations information to optimize pilot review and retention of relevant information, a method to more effectively signal a runway closure to pilots when at least one parallel runway remains in use, and modifications to airport surface detection equipment systems to detect potential taxiway landings and alert air traffic controllers.

Missed Steps

The NTSB investigation found that at about 2356 Pacific daylight time, Air Canada flight 759, an Airbus A320-211 was cleared to land on runway 28R at San Francisco International Airport. Instead, the pilots lined up with parallel taxiway C. A Boeing 787, an Airbus A340, another Boeing 787 and a Boeing 737 were on that taxiway awaiting clearance to take off from runway 28R.

The Air Canada Airbus that was involved in the incident. Source: WikimediaThe Air Canada Airbus that was involved in the incident. Source: WikimediaThe procedures for the approach to runway 28R required the first officer (as the pilot monitoring) to manually tune the instrument landing system (ILS) frequency for runway 28R, the NTSB said. Doing so would have provided backup lateral guidance (via the localizer) during the approach to supplement visual approach procedures.

However, when the first officer set up the approach, the NTSB said that he missed the step to manually tune the ILS frequency. The captain was required to review and verify all programming by the first officer but did not notice that the ILS frequency had not been entered.

The NTSB said in its report that the misidentification of taxiway C as the intended landing runway resulted from the flight crew’s lack of awareness that runway 28L was closed. The NTSB cited the crew's "ineffective review of the notice to airmen information" before the flight and during the landing approach.

A Case of 'Expectation Bias'

Runway 28R and Taxiway C at SFO, showing location of the four planes awaiting takeoff in the July 2017 incident. Source: NBC Bay AreaRunway 28R and Taxiway C at SFO, showing location of the four planes awaiting takeoff in the July 2017 incident. Source: NBC Bay AreaThe flight crew members stated, during post-incident interviews, that taxiway C resembled a runway. The NTSB said that although multiple cues were available to the flight crew to distinguish runway 28R from taxiway C (such as the green centerline lights and flashing yellow guard lights on the taxiway), enough cues also existed to confirm the crew’s expectation that the airplane was lined up with the intended landing runway (such as the general outline of airplane lights — in a straight line — on taxiway C and the presence of runway and approach lights on runway 28R, which also would have been present on runway 28L when open).

As a result, once the airplane was aligned with what the flight crew members thought was the correct landing surface, they were "likely not strongly considering contradictory information," the NTSB said. "The cues available to the flight crew to indicate that the airplane was aligned with a taxiway did not overcome the crew’s belief, as a result of expectation bias, that the taxiway was the intended landing runway."

The NTSB also said that although the flight crew’s work schedule for the incident flight complied with Canadian flight time limitations and rest requirements, the flight and duty-time and rest requirements for the captain would not have complied with U.S. flight-time limitations and rest requirements.

At the time of the incident, the captain had been awake for more than 19 hours, and the first officer had been awake for more than 12 hours, the NTSB said. "Thus," the NTSB report concluded that, "the captain and the first officer were fatigued during the incident flight."