SAN FRANCISCO (AP) — The Federal Aviation Administration is investigating why an Air Canada passenger plane ignored repeated orders by air traffic control at San Francisco International Airport to abort a weekend landing, officials said Tuesday. After landing safely, the plane reported a radio problem and Air Canada subsequently said the cockpit never received the orders. The Sunday night incident happened 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.