The steady growth of civil aviation has produced a corresponding increase in the size and complexity of the system for air traffic surveillance and control. To meet the operational demands forecast for the end of the century, it is anticipated that the system must not only continue to grow but also undergo a change in character, making a transition from a man-intensive to a machine-intensive system. It is foreseen that automation will be introduced to replace the human operator in several major areas such as surveillance, much decision making, and most communication. The role of man is expected to evolve into that of a manager of automatd processes, involving matching the capacity of system resources to the total workload imposed by demand, assigning of resources, assuring quality, and maintaining the operation of the system in the event of automated resource failure or malfunction.