...or should be.

If the assumption is that a hijacking creates a military threat to national security, then the focus becomes neutralizing the threat, not minimizing hostages. This means that if the flight crew / passengers can't subdue the hijackers, the plane wil be shot down. At least if it's over any potential target. That gives a good several thousand miles of the US that aren't too critical, but in general, it's going to be a lot tougher to get a free ride.