What stops elaborate or clever contraptions getting by and inciting chaos? The fact that 99.99% of people are not terrorists. Airport security checkpoints cann

What stops elaborate or clever contraptions getting by and inciting chaos? The fact that 99.99% of people are not terrorists. Airport security checkpoints cannot be considered a last stand against threats. It is one link in a chain including intelligence, passenger awareness, and aircraft design. The chain I describe is not security, but safety. "Screen for every potential danger" is not a viable goal for airport security. I prefer a statement like "decrease the likelihood of death (whoever's you care to measure) by 10x". While still vague, it gives some framework for comparing costs. To make up numbers, suppose for the same cost you could install backscatter machines and get a 10x reduction, or better radar infrastructure and get a 50x reduction. I know where I'd want my money. One externality here is the perception of safety. In some sense, it doesn't matter how good or safe flying is if people act (and spend...) as if every other plane were being bombed from the skies. But, I question if security gropes will really increase consumer confidence.