Odoni’s (1987) detailed description of the singleairport ground holding problem (GHP) as a dynamic and stochastic optimization problem stimulated much of the subsequent work. Important advances in modeling and solving the GHP are marked by the stochastic programming models of Richetta and Odoni (1993), the extension to a multiairport setting by Vranas et al. (1994), and the inclusion of en route constraints and rerouting options by Bertsimas and Stock (1998). Many other interesting papers on various aspects of optimizing ATFM and GHP appeared in the 1990s. Good reviews of the literature and of computational results can be found in Andreatta et al. (1993) and Hoffman and Ball (2000).