Column Generation Approaches to a Robust Airline Crew Pairing Model For Managing Extra Flights

The airline crew pairing problem (CPP) is one of the classical problems in airline operations research due to its crucial impact on the cost structure of an airline. Moreover, the complex crew regulations and the large scale of the resulting mathematical programming models have rendered it an academically interesting problem over decades. The CPP is a tactical problem, typically solved over a monthly planning horizon, with the objective of creating a set of crew pairings so that every flight in the schedule is covered, where a crew pairing refers to a sequence of flights operated by a single crew starting and ending at the same crew base. This paper discusses how an airline may hedge against a certain type of operational disruption by incorporating robustness into the pairings generated at the planning level. In particular, we address how a set of extra flights may be added into the flight schedule at the time of operation by modifying the pairings at hand and without delaying or canceling the existing flights in the schedule. We assume that the set of potential extra flights and their associated departure time windows are