SAN FRANCISCO • An Air Canada plane that nearly landed on a taxiway in San Francisco last month passed only 18m above the ground before aborting its approach and averting a crash, a US probe said.

The Canadian Airbus SE A320 may have missed one or more of the planes in its path on the ground by just a few metres in the July 7 incident. It was preparing to land not on the intended runway but on an adjacent taxiway, where other planes had lined up for take-off.

The pilots told National Transportation Safety Board (NTSB) investigators they thought they were about to land on one of two parallel runways at San Francisco's international airport. "They did not recall seeing aircraft on taxiway C" but "something did not look right to them", said an NTSB probe update.

The NTSB released radar plots showing where the planes were at various times and images from an airport surveillance camera that showed the Air Canada plane passing close to the jets on the ground. Although it was minutes before midnight, at least three of the planes on the ground were clearly visible.

While the NTSB has not yet calculated how close the planes came to a catastrophic collision, the Boeing 787 that was first in line on the taxiway has a tail that is almost 17m tall, according to the firm's website. That United Airlines plane had turned to enter the runway and the Air Canada jet appears to have passed just behind it, according to a radar plot released by NTSB.

The Air Canada pilots decided to climb away from the ground and abort the landing on their own, according to the NTSB.

The risk of collisions on the ground has been raised as a safety issue by the NTSB in the past. The highest death toll ever in an airline accident occurred on the ground when two Boeing 747s collided on a runway in 1977 in Tenerife, Canary Islands, killing 574 people.

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