Delay propagation and its implications in airline operations

Abstract

Airline companies try to increase their revenues, service level, and customer sat isfaction in the competitive airline industry. Airline schedule planning is very crucial for airline companies to reach their objectives. While they are planning their schedules, they expect that there will be no disruption. On the other hand, there are plenty of incidences such as weather conditions, mechanical failure, traffic, and security issues that cause delays and disrupt the operations of an airline. Even though it is impossible to avoid the delay completely, there are ways to decrease the propagation of the delay. To cope with delay propagation, airlines put idle time between flights. However, idle time means inefficient use of aircraft resources. Thus, adjusting the idle time in the schedule is a critical task for planning departments in different aspects. In this study, flight time rescheduling and aircraft swapping are used to decrease the expected delay propagation. By applying these two options, the scheduled slack in the schedule is clus tered at flights that are prone to propagate. It is aimed that the negative consequences of delay are reduced proactively while keeping total slack time in the schedule. Math ematical programming formulations the single layer model, the multi layer model, and the single layer model with swapping option are used. There is also an approximation for the single layer model with swapping option to overcome the computational issues. For the computational study, the flight schedule from Turkish Airlines is used. As a result, a decreased expected delay propagation is observed by rearranging the schedule without changing the cost of scheduled idle time.