The flight schedule is the central element of an airline’s planning process, aimed at optimizing the deployment of the airline’s resources in order to meet demands and maximize profits. In this paper, we present an overview of contributions to airline scheduling made by operations research professionals during the past 20 years or so. The overview follows the development of airline scheduling methodology from an early emphasis on standard quantitative optimization techniques to the recent trends toward a structured planning process in which all parts of the airline participate in the “construction” and “evaluation” of schedules, combining exact mathematical programming algorithms and heuristics.