and truly know what people have on them. now, that doesn't mean we're not going to stop it. we are going to stop a lot of things because of the way the backs scatter. different techniques we tried over the years. these are types of things you have to put in place. the oldest in terms of trying to prevent a bombing, you don't look for the bomb. you look for the bomber. behavioral assessment of officer, ability to spot what people are trying to do, getting on a plane. these techniques have evolved since 9/11. >> we were on a plane yesterday. i don't think we saw anything different. if you're a passenger flying in and out of the u.s., what are you likely to see now that there are new warnings. >> homeland security, some of is o vert, some is covert. they use cameras and supervisors. there's an array of passengers