Audio released of a San Francisco tower controller unsuccessfully ordering an Air Canada A320 to go around has raised concerns about the safety culture at the airline and is sure to cause investigations by the airline and regulators on both sides of the border.

Flight 781 from Montreal was ordered six times to abort a landing at SFO last Sunday but there was no acknowledgment from the crew and they landed at about 9:30 p.m. It was the second time in three months an Air Canada crew has been involved in a mishap at SFO. In Another A320 crew lined up to land on a taxiway with four aircraft lined up to take off and fortunately did hear the go around call before hitting any of them. The controller called the go-around because he was concerned another aircraft wouldn’t clear the runway in time. There was no conflict and it wasn’t until after the Airbus was on the ground that radio contact was reestablished on the same frequency.  One of the pilots reports a radio issue and the terse response from the controller is “that’s pretty evident.”

Controllers even shone a flashing red light toward the aircraft in a last-ditch effort to stop the landing but the SFO tower is at least two kilometres from the threshold of Runway 28R.

Air Canada and its pilots’ union focused on the radio problem in responses to reporters.

“After receiving proper clearance to land, it proceeded to do so and landed normally,” said airline spokesman Peter Fitzpatrick. “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 is investigating the circumstances.”

Air Canada Pilots Association spokesman Christopher Praught said the FAA is investigating a “communications failure after being cleared for landing.”