Construction lights were so bright they confused pilots of a fatigued Air Canada crew who nearly struck four aircraft on the ground while trying to land at night in July 2017 in San Francisco, according to preliminary reports.
The National Transportation Safety Board on Wednesday released more than 500 pages of investigative reports, including a video recording of the July 7 event, but didn't conclude what caused the airliner to come within feet of a catastrophe.
Both pilots reported feeling fatigue in the latter stages of their flight from Toronto. They were landing at about midnight local time, the equivalent of 3 a.m. where they had slept the night before, according to NTSB. The captain told investigators he may have gotten less than six hours of sleep and his rest had been disrupted by a late flight the previous night.
As the Air Canada plane approached the runway, the copilot thought something "didn't look right," he told investigators. But he wasn't certain what was wrong and was "unable to process what he was seeing."
The copilot told the captain, who was at the controls, to abort the landing and climb at about the same time the captain decided the same on his own, according to the NTSB. Seconds later, an air-traffic controller radioed a command to cancel the landing to the plane.
Pilots on a flight that had arrived four minutes earlier told investigators that "construction lights were so bright we could not determine the location" of the only runway open for landing that night. An adjacent parallel runway to the left of where they were cleared to land was under construction and closed.
Both pilots on the previous flight said they checked with their on-board instruments to ensure they were lined up for the proper runway.
The NTSB released a low-definition, black-and-white video recording that showed the Air Canada plane passing close to the planes on the ground, flying above or near two planes before climbing.
The Air Canada Airbus A320's pilots were supposed to land on the right of two parallel landing strips at San Francisco International Airport. Instead, they lined up to touch down to the right of that runway on a taxiway where four planes idled as they waited for permission to takeoff. The second parallel runway on the left side was closed for construction that night.
The incident came within feet of causing a fiery collision between two or more aircraft, according to NTSB data. The Air Canada plane was as low as 59 feet (18 meters) from the ground as the pilots aborted the landing and began climbing, according to earlier releases from the NTSB.
The tail on the Boeing 787 that was first in line on the taxiway is almost 56 feet high, according to the company's website. That United Airlines plane had turned to enter the runway and the Air Canada plane appears to have passed just behind it, according to a radar plot released by NTSB.
Next in line was a Philippine Airlines A340-300, a widebody jet with a tail that's about the same height or slightly higher than the 787's, according to Airbus' website.
The pilot of the United plane had tried to raise alarms about the Air Canada plane's flight path in air-traffic radio transmissions.
"Where's this guy going?" the pilot said. "He's on the taxiway," he added a few seconds later as the Air Canada plane passed just behind him.
For decades, the NTSB has warned of the risk of collisions on the ground. The highest death toll ever in an airline accident occurred in 1977 when two Boeing 747s collided on a runway in Tenerife, Canary Islands, killing 574 people.
One issue the NTSB is investigating is a warning system that tracks planes on or near the ground. The Federal Aviation Administration's air-traffic controller said the Air Canada plane disappeared briefly from the warning system's display shortly before passing over the other planes.
Unlike most accidents and incidents investigated by NTSB, there is no recording of cockpit conversations on the Air Canada plane. The device was overwritten during subsequent flights before it could be pulled from the plane, the NTSB said.