The cost of delay i s a serious and increasing problem in the airline industry. Air travel is increasing, and already domestic airports incur thousands of hours of delay daily, costing the industry $2 billion a year. One strategy for reducing total delay costs is to hold planes for a short time at the gate in order to reduce costly airborne congestion. In a network of airports involving hundreds of ights, it is dicult to determine the amount to hold each ight at the gate. This paper discusses how the optimization procedure simultaneous perturbation stochastic approximation (SPSA) can be used to process delay cost measurements from air trac simulation packages and produce an optimal gate holding schedule. As a test case, the SIMMOD air trac simulation package was used to model a simple four-airport network. Initial delay costs are reduced up to 10.3%.