Robust flight schedules through slack re-allocation

A myriad of uncontrollable factors in airline operations makes delays and disruptions unavoidable. To limit complexity, most conventional scheduling models, however, ignore the occurrence of unplanned events during operations. This leads to schedules that are vulnerable to delays and disruptions. In this work, we propose a flight schedule adjustment model that strategically re-allocates existing schedule slack to achieve a more robust schedule. Using data from an international carrier, we evaluate the resulting schedules using various performance metrics, including delay propagation and passenger delays. The results show that minor schedule adjustments to the original schedule can significantly improve overall schedule performance. In addition to the modeling contribution, we provide managerial insights obtained through extensive computational experiments. Unlike earlier works on slack re-allocation that focus primarily on demonstrating the effectiveness of the methods, our paper is, to our knowledge, the first one that also addresses a fundamental question pertaining to how airline characteristics and operations influence the strategy for robust scheduling.