Good article. I have walked onto a plane with either a Swiss Army Knife or my Leatherman tool kit (which contains a knife) more times than I can count. The Army knife, normally carried in a pocket, I usually just plain forgot to switch to my luggage. The metal detector overlooked it. The tool kit, carried in my belt pack, goes through the X-ray, but apparently doesn't look dangerous.

In my opinion, the best way to deal with this is arming the flight crew, maybe the flight attendants, and certainly a sky marshall or two. That, and make it more difficult to get into the cockpit. This is not hard to do.