The National Transportation Safety Board on Tuesday joined the investigation into an Air Canada flight that almost landed on a San Francisco International taxiway crowded with four other jetliners.
Air Canada flight 759, en route from Toronto with 140 passengers and crew aboard, had been cleared to land just before midnight Friday on runway 28R, according to the Federal Aviation Administration.
But the pilot lined up the Airbus A320 on a taxiway that runs parallel to the runway, where four fully loaded planes were queued up and waiting for clearance to depart, the FAA said.
A disaster was averted when air traffic control ordered the Air Canada pilot to abort the landing and circle around the airport for another try. The FAA is trying to determine how close the aircraft was to the ground and runway when the so-called "go-around" was performed.
As part of the investigation, the NTSB will review the approach for landing and interview air traffic controllers and possibly the pilots of the Air Canada flight. Though a crash was not involved, the agency has the authority to look into serious safety lapses.
Keith Holloway, an NTSB spokesman, said the agency probably would send investigators to San Francisco in the next few days.
Ross Aimer, a retired United Airlines captain, told the San Jose Mercury-News, which first reported the incident, that if the pilot had not been told to correct course, the scene would have been "horrific."
"If it is true, what happened probably came close to the greatest aviation disaster in history," Aimer said.
Peter Fitzpatrick, an Air Canada spokesman, said the airline did not have any new information about the incident to release Tuesday.
Audio from the airport's traffic control tower, which was archived online and reviewed by The Times, reveals more details of how the incident unfolded as the plane approached:
Air Canada pilot: Tower Air Canada 759 I can see lights on the runway there. Can you confirm we're clear to land?
Control tower: Air Canada 759 confirmed cleared to land on 28-right. There is no one on 28-right but you.
Air Canada pilot: OK, Air Canada 759
Unknown: Where is this guy going? He's on the taxiway!
Control tower: Air Canada, go around.
The FAA said the air traffic controller told the Air Canada jet to circle around and make another approach.
Air Canada pilot: Going around. Air Canada 759.
Control tower: Air Canada, it looks like you were lined up for Charlie there. Fly heading 280. Climb maintain 3,000.
Air Canada pilot: Heading 2-8-0. 3,000. Air Canada 759.
United pilot: United One, Air Canada flew directly over us.
Control tower: Yeah, I saw that guys.
The aircraft then landed at the airport without incident at 12:11 a.m. Saturday, about 50 minutes later than scheduled, according to the online flight path.
5:35 p.m, July 11.: This article has been updated with information on the NTSB's role in the investigation.