One has to look at the attributes of the attack and what it would have taken to carry this out.
Somehow whatever hardware was used to "hijack" the planes would have had to have been gotten onto the planes past security. People are making a lot of assumptions about what this hardware was (guns in the hands of wild-eyed fanatical humans, where somehow the guns and the fanatical humans got on the planes past airport security) which haven't been backed up by anything yet reported. What if there was no human terrorist on the planes and they were commandeered by remote control? Crazy tin-hat idea, but it's been a crazy day.
And they would have needed someone who could fly the planes with some precision - whether on or off the plane - to be sure of success. A pilot isn't going to obligingly fly the plane into a large civilian target - especially when they know they're dead either way.
Whatever hypothesis you go with, there was a lot - a whole lot - of sophistication behind this one. Not your usual truck bomb. This was really slick, a lot slicker that anything else seen.
And who benefited from it?
We should all keep our eyes and minds open, and be slow to make assumptions. Very strange, this one.
Hopefully the crash investigators will be looking hard for the black boxes, weapons, etc.
There are plenty of plastic and ceramic knives on the market that will pass through almost any security. The problem is honest people are at a disadvantage even when facing cowardly bastards like these Mohammedans, because the honest people aren't carrying a knife too. (Most people don't know how to use a knife anyway.)
This wasn't a breakdown in security. There is no way to keep every potential weapon off a plane. Even if you strip search every passenger the bad guys will just train in martial arts and use more scum bags to hijack the plane.
We used to put U.S. Marshals on flights back before we got metal detectors and xray machines at airports. We should go back to the "Sky" Marshal idea. Train them in the use of edged weapons and arm them with knives and guns. It worked fine in the past. It would work again.