Originally Posted by
RexBanner
At the end of the day we just have to accept that in life we live with some very sick people who have the potential to cause us harm. We can never get rid of this risk completely (...)
If someone wants to cause other people harm they will do, regardless of what we do.
It's true that we can't eliminate all risks completely, but that doesn't mean that some risks can't be eliminated, and the remaining risks reduced to the bare minimum. The simple step of requiring two crew members in the cockpit at all times (with appropriate procedures and training) is an example. Can be immediately implemented at an insignificant cost, and it would greatly complicate perpetrating this sort of thing.