The new scanning machines will see things like paper or plastic in your pocket, so they can definitely see a lot more than metal detectors. You may think that's

The new scanning machines will see things like paper or plastic in your pocket, so they can definitely see a lot more than metal detectors. You may think that's irrelevant, but it's not nothing. It's worth noting that 9/11 introduced a new threat that people hadn't really considered before: using planes as weapons. If you want to kill a bunch of people in the US there's lots of places with big crowds. A commercial airline r is a significant force multiplier: the OKC bombing killed "only" 168 people and the Las Vegas shooting only 68. 9/11 was an order of magnitude over that.