The cockpit voice recording from an Air Canada flight that nearly collided with several planes on a busy taxiway at San Francisco International Airport in July has been erased and experts say it could have been critical to the investigation.
The National Transportation Safety Board said in a statement released August 2 that the incident wasn’t reported to federal authorities until two days later and by then the data from the cockpit voice recorder had been erased.
“The incident airplane’s cockpit voice recorder had been overwritten, so NTSB investigators did not have that data,” the NTSB said.
WATCH: Only 30 metres separated an Air Canada plane from a ‘catastrophic’ accident
Experts say investigators have now lost vitally important information in uncovering what caused a mistake that could have led to the worst aviation disaster in history.
“Voice recorder data is always essential to any investigation,” retired United Airlines Capt. Ross Aimer, CEO of Aero Consulting Experts told Global News. “Basically the human factor part of it could have been perhaps solved by listening to fellas talking to each other that last minute. We would have perhaps found out what really caused these guys – a group of professional pilots – to make such a drastic mistake.”
Ross said that fatigue could have been a contributing factor that cause pilots to mistake a taxiway for a runway, but the voice recorder from the cockpit was never preserved.
“It is critical, without that information we may never fully discover what the cause of this was,” he said.
WATCH: Air traffic control audio captures panic as Air Canada flight nearly lands on taxiway
Just before midnight on July 7, Air Canada flight 759, with roughly 135 passengers on board, came within meters of hitting four passenger planes sitting on a taxiway, which the pilots thought was a runway.
The Air Canada jet, arriving from Toronto, was already on a landing approach when a pilot from another airline sitting on the taxiway alerted air traffic control.
The Air Canada pilot pulled up, and flew over the first two planes by just 30 metres. According to the U.S. Federal Aviation Administration, the Airbus A320 was sent around by an air traffic controller, and the plane “landed without incident” on a second approach.
“This could have been the worst aviation disaster in history,” Ross said. “Imagine an Airbus cartwheeling over four other aircraft full of fuel and passengers. We are talking over 1,500 casualties and five aircraft in flames.”
While Canadian officials were able to recover the flight data recorder, the NTSB said in a statement that the incident wasn’t reported to officials until July 9.
The Air Canada plane made several flights between July 8-10, according to the website flight aware, totalling more than 10 hours in the air. Cockpit voice recorders are only required to capture the last two hours of a plane’s flying time and are automatically overwritten unless the recordings are downloaded, experts say.
Air Canada spokesman Peter Fitzpatrick declined to comment, citing the ongoing investigation.
The pilots of the Air Canada Airbus A320 jet were very experienced, according to the NTSB, with the captain logging more than 20,000 hours of flying time, and the co-pilot had about 10,000 hours.
READ MORE: Air Canada travellers weren’t told their plane almost landed on crowded taxiway: passenger
The NTSB said the pilots told investigators “that they did not recall seeing aircraft on taxiway but that something did not look right to them.”
Aviation expert Mary Schiavo, a former Inspector General of the U.S. Department of Transportation, said the cockpit voice recorders capture conversations among the flight crew that is not recorded by air traffic control.
The agency reported that the pilot and co-pilot told investigators they mistook the runway 28-Right for 28-Left, and thought the taxiway that runs parallel to 28-Right was a clear runway.
But Schiavo said that runway lights are much brighter and a different colour than the taxiway lights and would be difficult for a pilot to confuse.
She added that incident wasn’t immediately reported to the NTSB by the pilots or air traffic controllers because the near-miss didn’t occur in the air and because the landing aircraft never made it to the ground meaning it’s not considered a “runway incursion.”
The NTSB said that investigations generally take 12 to 18 months to complete and that Air Canada, Transport Canada, and Air Canada Pilots Association have been appointed as “technical advisors.”
Transport Canada says it is assisting in the investigation.
“Transport Canada has assigned a technical advisor who will obtain factual information from the ongoing investigation, identify any issues relevant to the Minister’s responsibilities and coordinate the required support during the investigation,” a Transport Canada spokesperson said in an email.
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