Air traffic controllers told the pilots to pull up and go around.
The plane circled around and landed successfully on its second attempt, according to the FAA.
The FAA is now trying to determine how close the Air Canada aircraft came to the taxiway before pulling up.
Pilots and the control tower at San Francisco International Airport (SFO) can be heard remarking in astonishment as the AC759 narrowly misses them on the packed taxiway.
John Cox, an air safety investigator told CBC News there are electronic devices to help pilots line up with the runways for landing.
The flight was cleared to land on the appropriate runway but had lined up with the taxiway parallel to it where the other planes Saturday.
Next, a pilot from United Airlines flight 1, a Boeing 787 service to Singapore, tells controllers, "Air Canada flew directly over us".
Captain Aimer said that if the tower hadn't been able to swiftly redirect the Air Canada plane, disaster would have followed.
Currently, the United States government is exploring ways to "modernize" air traffic control in airports around the country. "There is no one on 28R but you", an air traffic controller responded. When air traffic control realizes the plane is headed for the taxiway, it is directed to go around and approach again.
"If you could imagine an Airbus colliding with four passenger aircraft wide bodies, full of fuel and passengers, then you can imagine how horrific this could have been", he said.
A spokesman for Air Canada said it is still investigating the circumstances of the incident.
'This is pretty huge, ' he said.
A spokesman for San Francisco's airport declined to comment. He just "lined up wrong", according to the FAA.
Thankfully, after the go-around, the Air Canada flight was able to land where it was supposed to successfully, despite TRYING TO LAND ON THE TAXIWAY MOMENTS BEFORE.
Airport authorities and the airlines involved are conducting an investigation.