The Next Generation Air Transportation System, or NextGen, is the transformation of the radar-based air traffic control system of today to a satellite-based system of the future. This transformation is essential in order to safely accommodate the number of people who fly in the United States. New, satellite-based technologies will significantly improve safety, capacity and efficiency on runways and in the nation's skies while providing environmentally friendly procedures and technologies that reduce fuel burn, carbon emissions and noise. The Federal Aviation Administration (FAA) is leveraging existing technologies and expanding their capabilities to bring the benefits of NextGen to the flying public today. This book provides an overview of the NextGen Air System, its implementation, phases of flight, and some of the technologies being used as its foundation.