A Robust Fleet-Assignment Model with Hub Isolation and Short Cycles

Airline decision makers cancel flights in operations because of disruptions. When canceling a flight, they usually cancel a cycle, a sequence of flights that begins and ends at the same airport. Consequently, a fleet assignment and aircraft rotation with many short cycles is frequently less sensitive to a flight cancellation than one with only a few short cycles. In this paper, we determine a lower bound for the number of short cycles using the hub connectivity of a fleet assignment, and we present fleet-assignment models (FAMs) that embed many short cycles and reduce hub connectivity within a solution. We show that solutions to such models perform better in operations than those of traditional FAMs that minimize planned operating cost and passenger spill.