Airline crew rostering: problem types, modeling, and optimization

Airline crew rostering is an important part of airline operations and an interesting problem for the application of operations research. The objective is to assign anonymous crew pairings either to personalized rosters or to anonymous bidlines which subsequently will be assigned to individual crew members. Compared to the crew pairing problem, crew rostering has received much less attention in the academic literature and the models presented have been rather simplified. The contribution of this paper is two-fold. First, we want to give a more comprehensive description of real-world airline crew rostering problems and the mathematical models used to capture the various constraints and objectives found in the airline industry. As this has not been attempted in previous research, we think it serves a purpose to reveal the complexity of real-world crew rostering to readers without industrial knowledge of the problem. Second, we want to present the solution methods employed in a commercial crew rostering system, in whose development we both have been involved. The Carmen Crew Rostering system is currently in use at several major European airlines including British Airways, KLM, Iberia, Alitalia, and Scandinavian Airlines (SAS) as well as at one of the world's largest passenger transportation companies, Deutsche Bahn (German State Railways). During the development of the Carmen Crew Rostering system, we have gained valuable experience about practical problem solving and we think the system constitutes an interesting case in the application of operations research.