There should be no assumed link between on-board speed sensors and the crash of Air France Flight 447 into the Atlantic Ocean last week, the airline’s chief executive said Thursday. “I am not convinced that the sensors are the cause of the accident,” said Air France Chief Executive Pierre-Henri Gourgeon. Still, he said, the airline will continue with a program, begun just days before the crash, to replace the sensors on its Airbus A330s, the same type of plane that crashed June 1.