A method of retrofitting a mechanically controlled aircraft with a fly-by-wire system includes removing a mechanical links between mechanical pilot inputs and actuators operable to drive flight surfaces. Electromechanical actuators are coupled between a plurality of vehicle management computers and the actuators. Each of the electromechanical actuators is operable to receive commands from the vehicle management computers and output a mechanical force to an input linkage of one of the actuators. Electromechanical pilot input modules are coupled to the mechanical pilot inputs. Each of the electromechanical pilot input modules is operable to convert a pilot-driven input force of an instance of the mechanical pilot inputs into an electronic signal indicative of the pilot-driven input force. At least one high performance computer is coupled to at least one of the vehicle management computers. The high performance computer executes one or more high level intelligence algorithms to selectively operate the aircraft autonomously.