Technologies to foil hijackers being considered include “onboard flight-control systems that could be programmed to prevent planes from heading into restricted areas; remote control from the ground that could not be overridden from the cockpit; and a panic button, also impossible to override, that has the plane direct itself to land at the nearest suitable field.”
However, these require adding expensive “fly-by-wire ” systems and improved computer, GPS, and communications reliability to be accepted by pilots.

The newest military remote-control aircraft systems are designed to let a single operator run four drones at once, with artificial intelligence that lets the drones make some decisions on their own.