Locked cabin doors are also good. Metal detectors at airports would be fine, if they were staffed by private security contractors rather than the unaccountable TSA. Also their xray backscatter machines are pointless, their paranoia about shoes is pointless, and their insane paranoia about water-bottles is pointless. Other countries don't have these things, and things are fine for them. By all means have people walk through a metal detector to stop carryon handguns, but the rest of this crap is completely pointless.