A simple queueing model of departure operations at congested airports is proposed. This model is calibrated and validated in the case of Boston Logan International Airport, using runway configuration and traffic data from the Airline Service Quality Performance (ASQP) data set. The model is then used to evaluate preliminary departure control schemes which use gate holding to alleviate congestion on the airport surface. The potential impact of these control schemes on direct operating costs, environmental costs and overall delay is quantified and discussed.