MONTREAL/WASHINGTON (Reuters) - Air Canada and the U.S. Federal Aviation Administration (FAA) said on Tuesday they are investigating a weekend flight that landed on a San Francisco runway after the crew was told to abort, the second recent incident involving the carrier at the busy California airport.

Air Canada Flight AC781, an A320 originating in Montreal, landed at San Francisco International Airport (SFO) on Sunday after receiving proper clearance only to learn that a subsequent message from air traffic control was not received by the crew, a spokeswoman for the airline said by email.

Air traffic control at SFO had instructed the Air Canada crew multiple times to execute a go-around because the controller was not certain that a preceding arrival would be completely clear of the runway before the jet was due to land, said FAA spokesman Ian Gregor.

ADVERTISEMENT

"The Air Canada crew did not acknowledge any of the controller's instructions," Gregor said by email.

"Upon landing, the crew was informed the tower had attempted unsuccessfully to contact the aircraft, however, the message was not received by the crew," Air Canada spokeswoman Isabelle Arthur wrote in a separate email.

The FAA was already investigating a separate incident from July after an Air Canada pilot lined up to land on a taxiway at SFO where four other planes were waiting to depart.

Gregor said a supervisor tried to alert Sunday's flight by using a red light gun to alert the plane to go around, as is standard practice when an air crew is not responding to radio instructions. Instead, the flight landed, as previously authorized, on runway 28R at 9:26 p.m. PDT (0626 GMT).

"After landing, the Air Canada crew told the tower they had a radio problem," Gregor said.

A radar replay showed the preceding arrival was in fact clear of the runway when Air Canada landed, he added.

ADVERTISEMENT

(Reporting by Allison Lampert in Montreal and David Shephardson in Washington, editing by G Crosse)