The one common characteristic of the models developed in this first stage is the implicit assumption of a single decision-making authority attempting to optimize a “global” objective function: The providers of ATFM services (e.g., the FAA in the United States, Eurocontrol in Europe) are responsible for the allocation of ground holding delays among individual flights and/or for the rerouting, if necessary, of flights. The objective is to optimize in the aggregate, e.g., by minimizing the overall direct operating costs associated with ground holding and rerouting decisions, summed over all airlines and aircraft. This, however, is an operating philosophy that airlines strongly disagree with. They correctly argue that only individual airlines have the infor mation necessary to make decisions on what is best for their own flights. As an obvious example, airline A, faced with a period of delays at a given congested airport, may assign very high priority to the timely arrival of one of its flights, X, because that flight may be carrying many business-class passengers who will be connecting to other flights or because it carries crews for subsequent flights departing from that airport. The assignment of priority to flight X has, in fact, little to do with direct operating costs of aircraft and is based on the business model of airline A and on infor mation that only A possesses