John T -
With the 720, was flown gear up at a low rate of descent into cutters that intetionally breached the fuel tanks. The experiment was to test a fuel additive that decreased a post crash fire. The intended crash landing was totally successful. The fuel additive was completely unsuccessful, as witnessed by the REALLY big post crash fire.
To fit a autofly/autoland system onto present commercial aircraft would be very expensive. A ground based cockpit/pilot taking over remotely would be very difficult considering the various types of aircraft that may have to be remotely controlled. Many aircraft are not even equipped with autoland, and even less with CATIIIc with rollout. Since remote live pilot would be impractical, there would need to be a L/VNAV navigation logic/takeover the autopilots that would fly the aircraft to the nearest CATIIIc runway (not a whole lot of those)and shoot the entire procedure. There would need to be extra circutry to lower the gear, flaps, arm speed brakes, and arm autobrakes. There would also need to be a complete disconnect of all circut breakers, cockpit switches, etc. to prevent a suicidal hijacker from simply turning off power to essential flight equipment/flight controls and other compenents. Even after all that a hijacker could destroy the pitot static system essential to the CADCs or go into the equipment bay and begin destroying LRUs.
While an admiral idea, remote/auto control of a commercial airliner would only be useful against incapacitation of both pilots, but still allow a suididal pilot to at least crash the aircraft and kill everyone on board, just maybe not at the place of his choosing.