Air Canada plane narrowly missed taxiing aircraft at San Francisco airport: NTSB

Air traffic controllers gave Air Canada flight 759 the go-ahead to land on runway 28-Right late on July 7, but the pilots lined up to land on a taxiway where four planes were awaiting takeoff clearance, according to the National Transportation Safety Board.

The Air Canada plane flew within just a few dozen feet over the first plane lined up for takeoff, a United Airlines Boeing 787, before an air traffic controller told the Air Canada pilots to go around.

"United 1. Air Canada flew directly over us," a United Airlines pilot told air traffic controllers moments after the incident, NPR reported.

“Yeah, I saw that, guys,” the controller responded.

"Where's this guy going?" another pilot asked air traffic controllers, according to a radio call obtained by NPR. "He's on the taxiway!"

The Air Canada pilots told investigators they both believed the Airbus A320 was lined up for landing on 28R, and not the taxiway, when they descended around 11:45 p.m. They said that they “did not recall seeing aircraft” on the taxiway.

Still, they said, “something did not look right to them.” They double checked with air traffic controllers at least once to be sure they were landing on the right runway and were told that they remained clear to land on runway 28R, according to the NTSB.

The pilots said they believed that the lighted runway on their left was 28-Left and that they were lined up for 28R, however, 28L had been closed for construction and did not have any lights on. Instead, a 20.5-foot wide lighted, flashing X was placed at the threshold, marking the runway as closed.

Officials continue to investigate why the mix-up happened. Investigators said that at the time of the near collision, the taxiway was lit with blue lights to distinguish it from the white lights of the runway.