Questions continue to swirl around a new issue involving an Air Canada flight landing at San Francisco International Airport.
The pilot for Flight 781, an Airbus 320, on Sunday failed to respond to air traffic control's warning not to land on the runway because it was not clear whether another jet was still on that runway. It's the second incident involving an Air Canada jet at SFO in the past six months. A spokesperson confirmed to NBC Bay Area Tuesday there were two different pilots involved in the incidents.
The Federal Aviation Administration said air traffic control cleared Flight 781 to land on the runway, but then noticed a preceding arrival might not clear the runway in time.
In air traffic recordings, the tower repeatedly calls for the Air Canada jet to "go around." The FAA said the crew did not acknowledge the controller's instructions.
A supervisor in the tower then used a red light to alert the crew to go around, which is standard protocol when a crew is not responding to radio instructions. But the pilot did not acknowledge the red light alert as well.
After landing the pilot told the tower his radio had malfunctioned.
Aviation experts said there are some big questions that need to be answered.
"They usually have two radios," aviation expert Mike McCarron said. "All back up was there, but it didn't kick in."
In July, the FAA said an Air Canada pilot almost landed on the taxiway instead of the runway at SFO. In response to the close call, the FAA issued new rules for nighttime landings and control-tower staffing at SFO.
Keith Rayle, a former Army pilot, said he will still catch his flight with Air Canada, but passengers should get answers on what went wrong in both incidents.
"It's unusual that would happen," Rayle said. "Flashing red means you shouldn't land. That's flying 101."
The FAA is investigating both incidents.