Many major airports experience aircraft delays caused by increasing aviation activity and decreasing airfield capacity. But the traditional solution to the problem--building new airports or expanding existing ones--is often infeasible because of environmental, financial, or institutional constraints. Instead, managing demand or improving operational efficiency seens to offer the best opportunities for relieving airport congestion. We discuss the quantiative techniques available for evaluating the merits of managing demand or improving operational efficiency and then describe our preferred technique--an airfield simulation model. An airfield simulation model requires a large data base, but its output can be selected and tailored to individual situations. It can be used to investigate different elements of the airfield and to provide the finest level of detail for short-term planning and summary outputs for analyzing longer term problems./Author/