The Federal Aviation Administration is investigating why an Air Canada plane ignored repeated orders by an air traffic controller at San Francisco International Airport to abort a landing over the weekend.

The Sunday night incident comes three months after another Air Canada jet with 140 people on board nearly landed on a crowded taxiway at San Francisco's main airport. The close call in July prompted the FAA to issue new rules for nighttime landings and control tower staffing at the airport.

FAA spokesman Ian Gregor said Tuesday that the latest incident involved Air Canada Flight 781 from Montreal which was given initial clearance to land. But air traffic control then gave multiple orders to "go around'' because it believed another plane may have been in the runway.

Gregor said that the crew acknowledged the tower's initial clearance to land but did not respond to the subsequent orders. After landing safely, "the Air Canada crew told the tower they had a radio problem,'' Gregor said in an emailed statement, adding that the FAA was investigating.

Dramatic audio from San Francisco airport tower as Air Canada flight fails to heed landing instructions 0:26

Air Canada spokesman Peter Fitzpatrick said the company also was investigating the incident.

"After receiving proper clearance to land it proceeded to do so and landed normally. Upon landing the crew was informed the tower had attempted unsuccessfully to contact the aircraft, however the message was not received by the crew,'' Fitzpatrick said.

Control tower orders 'go around' after plane nearly lands on taxiway with four planes waiting 0:31 In July, an Air Canada jet descended toward a taxiway holding four other planes rather than its assigned runway. The Air Canada pilots descended to less than 100 feet above the ground and flew over another plane before aborting the landing.

In August, the FAA issued new procedures to apply when a runway parallel to a plane's designated runway is closed, as it was July 7, possibly contributing to the confusion.

When an adjacent runway is shut down at night, air traffic controllers will no longer let pilots make so-called visual approaches to land. Instead, they must use instrument landing systems or satellite-based systems to line up for the correct runway, according to the new rules.

The FAA said the agency also will require two controllers in the airport tower during busy late-night periods. Only one controller was working during the Air Canada incident in July.