> I think you're underestimating the havoc that a group of well-trained individuals armed with knives could cause in the middle of a transcontinental flight even with a locked, reinforced cabin door.

Of course they can do a lot of damage. But they don't have to be on a plane for that. They can do a lot of damage on the street. The big question is: can they take control of the plane and use it as a weapon?

Nowadays, passengers know that hijacking means likely death. That knife won't stop everybody.