This book discusses the practice of no-fly zones in international affairs. The first no-fly zone was imposed over northern Iraq immediately after the first Gulf War, and since then they have become a regular recourse for policymakers confronted with humanitarian crises. They have come to be viewed as a feasible, essentially non-violent form of intervention that can be performed entirely from the air in a situation where some form of action is widely thought to be necessary but the political will for a ground operation is insufficient. Nonetheless, even among policymakers, there is limited understanding of the requirements, the shortcomings, and the potentialities of no-fly zones. This is the first comprehensive work on this topic and examines the assumptions surrounding no-fly zones by focusing on issues such as authority, cost, the possibility of escalation, and effectiveness.