SFO (CBS SF/AP) — The NTSB on Tuesday announced it is investigating a close call at SFO last week where an Air Canada jet nearly landed on a taxiway that was packed with other planes.

The Federal Aviation Administration is also investigating why the pilot mistakenly made his approach toward the taxiway instead of the runway just to the left.

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The incident happened just before midnight on Friday when other pilots sounded the alarm and possibly prevented a horrific accident.

Air Canada flight 759 with 140 people on board was coming in front Toronto. The Airbus A320 was cleared to land on runway 28R at SFO, but instead lined up with a taxiway that parallels the runway.

There were four other airliners on that taxiway waiting to take off.

Air traffic control audio captured what happened next:

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 28R. There is no one on 28R but you.

Air Canada pilot: Okay 759

Unknown: Where is this guy going? He’s on the taxiway!

Control tower: Yeah, I saw that guys.

The tower ordered the Air Canada pilot to abort the landing.

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Roughly 30 seconds later, a United Airlines pilot on the taxiway says the jet “flew directly over us.”

FAA spokesman Ian Gregor would not comment on how close Air Canada Flight 759 came to disaster, citing the ongoing investigation.

“Somebody wasn’t paying attention,” retired airline pilot Dick Deeds told KPIX 5. “It blows my mind, to be honest. The only thing I can think of is the possibility of fatigue.”

Deeds flew in and out of SFO hundreds of times and logged more than 30,000 hours in the sky.

“If it’s a clear night, you’re looking out the window, you see the runway, the yellow lights. You see the blue lights,” said Deeds.

As this investigation unfolds, it is terrifying to think of what could have happened.

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“Probably one of the worst in aviation history,” said Deeds. “He would probably hit the first one and the second one, and it would be more than one aircraft in the accident.”