The Federal Aviation Administration (FAA) is in the midst of the largest air traffic management system upgrade in its history. To consider first a future system in which ground-based air traffic facilities retain control of airspace and traffic, there are several possibilities with respect to human roles and tasks. Center-terminal radar approach control automation system is a time-based system that when fully implemented contains three modules: a traffic management advisor, a descent advisor, and a final approach spacing tool. In the United States, the FAA's enhanced traffic management system will improve the ability of the air traffic control (ATC) System Command Center to manage traffic in cooperation with traffic management units at each en route center and system operations center at airlines. Ongoing attempts to make air traffic management more effective can, and should, point the way to the shape of the future tactical ATC system.