Forecasts of civil aviation growth indicate the need for long-term improvements in the nation's airports and air traffic control (ATC) system to safely and efficiently accommodate increased air traffic. This report estimates the major benefits (other than direct cost changes) arising from increased terminal area capacity and improved aviation safety. The study compares aircraft delays in the terminal area and aviation accidents that would be expected with (1) the current ATC system, (2) the Upgraded Third Generation ATC System described in the current FAA Ten Year Plan (1973-1983), and (3) the Advanced Air Traffic Management System (AATMS). The conclusions are (1) that an ATC system such as AATMS should yield major reductions in airplane delays at terminal areas, but that to minimize such delays in the 1990s and beyond it will also be necessary to expand and improve facilities at many of the major airports, and (2) that an AATMS could potentially prevent nearly a quarter of the fatal general aviation accidents that might otherwise occur, and that either the AATMS or the Upgraded Third Generation ATC System could potentially prevent nearly a third of the fatal accidents that might otherwise occur in certificated air carrier operations. 165 pp. Ref.