Dynamic Airline Fleet Assignment and Integrated Modeling

Fleet assignment is a major decision problem of the airline planning process. It assigns fleet types to scheduled flights while maximizing profit. Basic fleet assignment models (FAM) are solved irrespective of other planning steps. Although this yields an optimal assignment solution, it might cause feasibility or profitability issues in dependent planning steps. We provide an overview of strategies for integrating fleet assignment and at least one further planning step. Traditionally, FAMs do not revise their solution if demand and thus profitability deviates from expected values. We present dynamic fleet assignment which comprises both assigning fleet types based on expected values of demand and demand-driven re-fleeting. Further, we incorporate robustness into the FAM which increases re-fleeting flexibility. Additionally, we propose an extension of an existing robustness concept. A dynamic fleet assignment process for a medium-sized schedule is simulated in computational experiments. The results demonstrate that for a large demand variation using a robust fleet assignment leads to higher re-fleeting profits than applying a non-robust model. Further, our proposed robustness strategy largely outperforms the traditional robustness concept.