Originally Posted by
KenV
Lock systems only work if there are one or two owners/operators. Airplanes have dozens and even hundreds of operators making any lock system simply untenable.
Any idea with locks fails when the person allowed to have a key - which this person was - is the one that wants to use the aircraft for a visible suicide. As we saw with German Wings this could be a first officer. Security with wetware always eventually requires trust - there will always be people that breach that trust.