[5by5]

Um...OK. So are you saying that we should have a completely pilotless system then? Or that there are easier ways to implement an "override" than being able to control the plane from the ground. F-16s, armed flight crews, isolating the flight deck, etc. If so, I agree.

My argument is that implementing a ground based override system is needlessly complex and introduces far more potential problems than it purports to solve.

[annalex]

I am saying that a wholly pilotless system is technically feasible, but would be fragile, impractical, and serve no useful purpose. An override from the ground for emergency purposes is feasible and desirable, as it will prevent or mitigate 9/11 type of disasters. It should be implemented and used before the method of last resort -- shooting the plane down -- is used. A malicious attack on such system in order to cause airliners to nosedive is not feasible since only a few people need to have access to the keys, just like the presidential "football".