[frevd]

No. It is certainly not my intention to make fun of the case that a copilot is able to control a machine and crash it at his will. Lufthansa is saying "there is no system that can prevent this kind of incident". They will have to take the possibility into account that you have to protect the plane against an authorized person as well, and think about possible solutions to this problem. Solving conflicting interests is not an easy task.

[frevd]

In summary, there must be mechanisms to de-authorize personal, by means of majority vote. To prevent an attack vector, biometric systems need to be used to verify other authorized personal safely (it might be far fetched, but measuring certain stress hormons might prevent attackers from controlling authorized personal and using them to override controls as well, and likewise, other authorized people must be able to act, e.g. by having controls that cannot be blocked by any means (re voice recorders all over the plane to enable or disable locks etc, again by majority vote)). Does that sound too futuristic? I wouldn't want to board a plane if I cannot be sure that any and all cases are covered.