The FAA is planning and coordinating R&D for the next generation air transportation system (NextGen). Transitioning to the NextGen will require FAA to continue to acquire new air traffic control (ATC) systems on schedule and on budget. NextGen includes system acquisitions but is a significantly larger initiative involving multiple federal agencies, such as NASA, which conducted aeronautics R&D for NextGen, and non-federal aviation stakeholders, such as aviation equipment manufacturers, airports, and aircraft operators. This report addressed: (1) FAA¿s ATC systems acquisition activities; (2) key NextGen planning and transition issues; and (3) key challenges that FAA faces in implementing NextGen. Illustrations.