If multiple communication systems aboard Malaysia Airlines Flight 370 were manually disabled, as investigators increasingly suspect happened, it would have required detailed knowledge of the long-range Boeing Co. 777's inner workings.
The first loss of the jet's transponder, which communicates the jet's position, speed and call sign to air traffic control radar, would require disabling a circuit breaker above and behind an overhead panel. Pilots rarely, if ever, need to access the circuit breakers, which are reserved for maintenance personnel.
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The shutdown of the on board reporting system shortly after the jet was last seen on radar, can be performed in a series of keystrokes on either of the cockpit's two flight management computers in the cockpit. The computers are used to set the performance of the engines on takeoff, plan the route, as well as other functions to guide the 777.
After vanishing, the jet's satellite communications system continued to ping orbiting satellites for at least five hours. The pings ceased at a point over the Indian Ocean, while the aircraft was at a normal cruise altitude, say two people familiar with the jet's last known position. Investigators are trying to understand that loss, and whether or not "something catastrophic happened or someone switched off" the satellite communication system, says one of the people.
A physical disconnection of the satellite communications system would require extremely detailed knowledge of the aircraft, its internal structure and its systems. The satellite data system is spread across the aircraft and disabling it would require physical access to key components. Disconnecting the satellite data system from the jet's central computer, known as AIMS, would disable its transmission. The central computer can be reached from inside the jet while it is flying, but its whereabouts would have to be known by someone deeply familiar with the 777.
