Last week, a man with a rifle shot three Transportation Security Administration agents at Los Angeles International Airport, killing one. This episode evoked the same response as every other aviation attack: the impulse to devise a quick solution. The union representing TSA employees urged that at least some security screeners be armed—a request administrator John Pistole promised to consider. The driving assumption is that you can never be too careful. But you can, of course. Training TSA agents to carry firearms would cost money, invite terrorists to locate their massacres elsewhere in the terminal, and not necessarily save a single life. Besides, points out Steve Chapman, equipping screeners with deadly weapons would also heighten the sense of coercion and intrusion that makes air travel resemble admission to a medium-security prison.