SAN FRANCISCO — The wayward Air Canada pilot who nearly landed on a crowded SFO taxiway earlier this month did not activate his computer guidance system that would have helped guide his airplane onto the appropriate runway and not dozens of feet from a catastrophe, according to a source familiar with the federal investigation.

Preliminary findings in the joint Federal Aviation Administration and National Transportation Safety Board investigation have determined that the pilot — who flew for his carrier again the next day after his aborted July 7 landing — did not activate his Instrument Landing System during his visual approach, the source said. The Wall Street Journal, citing two unnamed sources familiar with the investigation, also reported Air Canada flight 759 attempted to land manually with no back-up.

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NTSB: Air Canada close-call at SFO was even worse than first reported In what experts have called a near-disaster, the Airbus 320 passed over two fully loaded airplanes on the taxiway, as close as 51 feet to one, according to flight data information analyzed by this newspaper, before finally climbing to abort the landing and traveling over two more aircraft. The NTSB and FAA have interviewed the Air Canada flight crew and SFO air traffic controllers.

With the clear weather that night, retired United Airlines pilot Ross Aimer said that, based on air traffic audio, the Air Canada pilot was approved for a Flight Management System (FMS) visual to Runway 28-Right, which would not require him to use his computer guidance system. That is an angled approach that would require adjusting the guidance equipment if he chose to use it.

Aimer said most pilots don’t use the guidance equipment under those conditions and that type of approach.

NTSB and FAA officials have declined to comment on the ongoing investigation, although an NTSB official said investigators have finished their on-site probe at SFO.

Aimer has also said that based on radio traffic and sources, only one SFO air traffic controller was working the ground and tower frequencies the night of the close-call. Right before the controller called for Air Canada to “go around,” he had been dealing with another facility, investigators have reported.

A retired SFO air traffic controller who worked there for 21 years, Mark Nelson, said at that time of day and with that type of weather, there would typically be two air traffic controllers on duty, but it’s possible one controller was handling all those duties.

“It’s a judgment call based on the volume of traffic,” Nelson said. “One controller could easily handle that amount of traffic.”

Nelson also said it would be difficult for the controller to notice anything odd visually with the approach.

“There’s no way with the naked eye at midnight you can see in the dark if they are lined up on 28-Right or the taxiway,” Nelson said.

Nelson questioned why the Airport Surface Surveillance Capability system, which monitors runway traffic and incoming jets, didn’t alert the tower when the Air Canada airplane was veering so far off course. The system would normally alert the tower through a loudspeaker, he said.

Nelson has seen a lot during his air traffic controller career, but when he watched the Bay Area News Group video re-creation of the landing using flight data records and audio, he was shocked.

“It was worse than I anticipated,” Nelson said. “This one was pretty ugly.”

Just three days before the near-miss, the Air Canada Pilots Association, which represents this captain, released a statement lambasting the Canadian government’s proposed regulations on flight hours for pilots to combat fatigue, pointing to recommendations set by the U.S. space agency, NASA.

“The government’s failure to recommend well-established science and international best practices that have helped advanced aviation safety across the globe will adversely impact Canadian aviation for years to come,” said Capt. Dan Adamus, Canada’s representative of the Air Line Pilots Association. “The government has delayed updating fatigue regulations for far too long, and it is entirely unacceptable that most airlines will have up to four years to implement.”

The Air Canada flight from Toronto to San Francisco was a red-eye that landed in SFO around midnight, or 3 a.m. local time in Toronto.

Union spokesman Chris Praught said that because of the ongoing probe, he was limited in his comments, and could not comment on the pilot’s status and flight hours.

“It is a testament to the expertise and professionalism of the highly trained crew that they were able to ensure that the flight arrived safely at its destination,” he said.