Defining, measuring, and predicting airspace capacity

One of the key problems facing the managers of the National Airspace System in the United States involves the defining, measuring, and predicting of airspace capacity. The difficulty surrounding this task is due primarily to the numerous variables that affect airspace capacity and the subjective nature of many of them. The problems surrounding the concept of airspace capacity are outlined, and some of the factors that must be recognized before one can hope to deal with the problem in a useful way are identified.>