Flight delays have beset the U.S. national airspace system. In 2007, more than one-quarter of all flights either arrived late or were cancelled across the system, according to the Department of Transportation (DOT). DOT and its operating agency, the Federal Aviation Administration (FAA), are making substantial investments in transforming to a new air traffic control system, the Next Generation Air Transportation System (NextGen); a system that is expected to reduce delays over the next decade. This book explores the extent to which flight delays in the U.S. national airspace system have changed since 2007 and the contributing factors to these changes. Also discussed are the actions the DOT and FAA are expected to make that will reduce delays in the coming years.