American engineers do not cease their efforts to find a solution to a difficult problem – how to prevent a passenger airliner from plunging into a skyscraper even if the pilot strives to do this. The most radical solution was immediately realized and air-defense complexes were deployed around Washington and other large cities of the country.
The specialists of Northrop Grumman proposed a more humane solution – to provide passenger aircraft with a control system used to control the flight of a heavy unmanned aircraft Global Hawk. This would make it possible to switch over the aircraft control to a ground-based control center and even to remotely land the aircraft. However, this solution also has some disadvantages. Remote control requires a stable radio communication with the aircraft and if terrorists capture the ground-based control center, the consequences will be deplorable.
Edward Lee from the Californian University in Berkley proposed an alternative solution that is close to the ideal solution. The aircraft control system itself must resist to any attempt of the pilot to direct the airliner to a certain"forbidden" zone. It will automatically divert the aircraft from a dangerous course as soon as the pilot attempts to reach the forbidden zone. The system reaction force will depend on the pilot's resolution.

The forbidden zone looks as if it is surrounded by soft walls that push off the aircraft but do not cause a crash. For this purpose, the geographical values of all forbidden zones will be entered in the database and an on-board computer will control the flight. As soon as the system detects an attempt to jam their signals, it will automatically switch over to another navigational system based on radio beacons. The system operates automatically, independently of the ground-based control centers. To use it, it is only necessary to slightly change the on-board software of aircraft.

By New Scientist.