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An Air Canada pilot had been awake for over 19 hours when his plane had a near miss at San Francisco International Airport (SFO) on the night of July 7, 2017.

That was just one factor that led to an incident that was the subject of a review by the U.S. National Transportation Safety Board (NTSB), which released on Tuesday an abstract of a longer report it plans to roll out in “several weeks.”

Coverage of Air Canada on Globalnews.ca:

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The incident unfolded at about 11:56 p.m. PT, as Air Canada flight 759, which was coming from Toronto, made its approach into SFO.

The plane had been cleared to land on runway 28R, but it lined up with taxiway C, a parallel strip.

There were four airplanes on that taxiway at the time — two Boeing 787s, a Boeing 737 and an Airbus A340 — that were waiting to take off from runway 28R, the NTSB’s report said.

READ MORE: Security video shows Air Canada’s near-miss on crowded San Francisco airport taxiway

The Air Canada plane, which was carrying 135 passengers and five crew, was flying at an altitude of about 100 feet (30.5 metres) when it cleared the first airplane on the taxiway, and was flying at about 60 feet (18.3 meters) when it missed a second.

At that time, the flight “initiated a go-around” and started climbing.

No one on the plane was hurt, and the aircraft didn’t sustain any damage.

Nevertheless, numerous factors led to the incident.

One was that the captain, a reserve pilot, failed to take note of the fact that runway 28L, another runway at SFO, was scheduled to be closed at 11 p.m. that night.

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Another was that the first officer didn’t tune the plane’s instrument landing system (ILS) for runway 28R, which would have given the flight crew “backup lateral guidance to supplement the visual approach procedures.”

In this Oct. 24, 2017 file photo, an Air Canada plane prepares to land on a runway at San Francisco International Airport in San Francisco. AP Photo/Jeff Chiu, File

But one factor that the NTSB focused on — and which gained attention from the Air Canada pilots’ union — was the flight crew’s fatigue.

The NTSB noted that the flight crew started feeling tired after they had flown through thunderstorms that had taken place at about 9:45 p.m. PT.

The incident, the safety board noted, took place at about 11:56 p.m., and that was actually 2:56 a.m. according to the flight crew’s “normal body clock time.”

“Thus, part of the incident flight occurred during a time when the flight crew would normally have been asleep (according to postincident interviews) and at a time that approximates the start of the human circadian low period described in Air Canada’s fatigue information,” the report said. Tweet This

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The report went on to note that the pilot had been awake for over 19 hours, and the first officer for over 12 hours.

“Thus, the captain and the first officer were fatigued during the incident flight,” the report said.

READ MORE: Air Canada flight told to abort landing 6 times over fear of plane on tarmac, lands anyway

The NTSB called for revisions to Canadian regulations that would “address the potential for fatigue for pilots on reserve duty who are called to operate evening flights that would extend into the pilots’ window of circadian low.”

It noted that the flight crew’s work schedule was within “applicable Canadian flight time limitations and rest requirements,” but that “flight and duty time and rest requirements” for the captain “would not have complied with U.S. flight time limitations and rest requirements.”

The NTSB went on to say that Transport Canada’s regulations around flight and duty time date back to 1996.

The agency proposed new regulations in 2014, revising them in 2017 — but never finalizing them.

Ultimately, the NTSB recommended that Transport Canada “revise current regulations to address the potential for fatigue for pilots on reserve duty who are called to operate evening flights that would extend into the pilots’ window of circadian low.” Tweet This

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That recommendation drew enthusiastic support from the Air Canada Pilots’ Association (ACPA).

“Their findings on fatigue underscore the many years of urgent calls by Canada’s pilots for flight crew fatigue rules that are supported by science,” it said in a news release.

The union cited NASA research and said, “the science is clear: fatigue is a form of impairment.

It called on the federal government to limit duty periods for night flights to 8.5 hours of flying time, and to make sure that pilots on all aircraft sizes “have the same protective fatigue limits, implemented at the same time.”