Routing and scheduling models for robust allocation of slack

A myriad of uncontrollable factors in airline operations make delays and disruptions unavoidable. Most conventional scheduling models, however, ignore the presence of uncertainties in actual operations in order to limit the complexity of the problem. This leads to schedules that are prone to delays and disruptions. As a result, there has been wide interest recently in building robustness into airline schedules. In this work, we investigate slack allocation approaches for robust airline schedule planning. In particular, we propose three models: aircraft re-routing model, flight schedule re-timing model, and block time adjustment model, together with their variants. Using data from an international carrier, we evaluate the impacts of the resulting schedules on various performance metrics, including passenger delays. The results show that minor modifications to an original schedule can significantly improve the overall performance of the schedule. Through empirical results, we provide a comprehensive discussion of model behaviors and how an airline's characteristics can affect the strategy for robust scheduling.