We present a theoretical model of airport searches. The model extends previous work in the area in that detection conditional on search is imperfect. The hit rates tests for racial bias developed in Knowles, Persico, and Todd (2001) is shown to apply even in the presence of imperfections in monitoring. We then study two channels for improving airport security: better targeting and better detection. We show that better targeting does not necessarily decrease the overall crime rate, although it will decrease crime in the group that is targeted. Improved detection rates unambiguously decrease crime. Group-specific improvements in detection do not necessarily increase the number of searches for those groups. The analysis is extended to allow for the possibility that criminal passengers disguise themselves as members of low-crime groups.