Profiling
Or suppose he disguises himself as a white poodle? Or wears a Hogwarts invisibility cloak? Get serious.
Profiling works under certain conditions. Granted, a blue-eyed blond might blow up a plane--one certainly blew up a building in Oklahoma--but under the current special circumstances it isn't likely. Airport officials who are currently searching kids and little old ladies are being imbeciles and risk sacrificing thousands on the cross of political correctness.
Please check out this page and get a clue.