The driver for the adoption and implementation of the CDM concept was a small, OR-minded team in the FAA, the U.S. Department of Transportation, and especially the Metron Corporation (Chang et al. 2001). The CDM Program has already led to major reductions in delays and missed connections for air travelers and to documented savings of hundreds of millions of dollars in airline operating costs. ATFMrelated OR research has concurrently shifted away from large-scale, aggregate optimization models and toward “real-time” decision support tools that assist air traffic managers in the FAA and Airline Operations Centers in taking maximum advantage of the massive, up-to-date information base that CDM has made available. It is important to note, however, that many of the ideas and formulations developed in the