We analyze the case of protecting an airport, in which there is concern with terrorist threats against the Air Trac Control (ATC) Tower. To deter terrorist actions, airport authorities rely on various protective measures. They have considerable costs, but by deploying them, airport authorities expect to minimize the risks of terrorist actions. We aim at giving advice to the airport authorities by devising a security resource allocation plan. We use the framework of adversarial risk analysis to deal with the problem.