US investigators think that the plane continued to fly for some four hours after losing contact with air traffic controllers, based on data from the plane’s engines that was automatically downloaded and transmitted to the ground as part of routine maintenance programs. They speculate that a pilot or someone else on board may have intentionally disabled the craft’s transponders to avoid detection and divert the plane. The signals, or “pings,” were sent to a satellite for four hours after the plane dropped out of contact, according to a US official. Boeing offers a service that allows an aircraft to send a stream of data to a satellite during a flight that gives information about the aircraft’s functioning. Malaysia Airlines does not subscribe to that service; according to the official, the plane was attempting to initiate contact with the satellite.