The world's busy air traffic corridors pass over hundreds of volcanoes capable of hazardous explosive eruptions. The risk to aviation from volcanic activity is significant. In the United States alone, aircraft carry about 300,000 passengers and hundreds of millions of dollars of cargo near active volcanoes each day. Costly disruption of flight operations in Europe and North America in 2010 in the wake of a moderate-size eruption in Iceland clearly demonstrates how eruptions can have global impacts on the aviation industry. This book examines national and international efforts, and partnered with the U.S. Geological Survey Volcano Hazards Program, which is playing a leading role in the global effort to reduce the risk posed to aircraft by volcanic eruptions.