Current aviation security procedures screen all passengers uniformly. Varying the amount of screening individuals receive based on an assessment of their relative risk has the potential to reduce the security burdens on some travelers, while improving security overall. This paper examines the security costs and benefits of a trusted traveler program, in which individuals who have been identified as posting less risk than others are allowed to pass through security with reduced security screening. This allows security resources to be shifted from travelers who have been identified as low risk, to the remaining unknown-risk population. However, fears that terrorists may exploit trusted traveler programs have dissuaded adoption of such programs. This analysis estimates the security performance of a trusted traveler program in the presence of attacker attempts to compromise it. It finds that, although these attempts would reduce the maximum potential security benefits of a program, they would not eliminate those benefits in all circumstances.