Shoot the uniforms.

http://www.washingtonpost.com/wp-dyn/articles/A947-2002Aug9.html "The pilots' union is calling for the TSA to create a new airport badging system using a biometric component, such as iris scans or fingerprints, to verify the identity not only of pilots but also of any armed federal agents who may be on a flight. Meanwhile, Luckey has sent pilots tips on counter-surveillance techniques, such as how to sneak a photo of a suspicious person. Stalking incidents, like thefts of uniforms, are "demonstrably a very viable threat and something we need to guard against," he said."