Nope, can't happen. As one of thee earlier posters mentioned aircraft systems are not "online". Even if someone was able to hack directly into the e and e bay compartment (avionics/electronic systems) which is below the cockpit, pilots are still able to bypass or disconnect the electronic systems and fly old school. The engine thrust levers on the newer aircraft are fly by wire instead of a direct cable link in the older models, however this system is fully isolated within the engine and isolated from all other equipment.