Optimising for Sustainability as an Objective Function Within Airline Fleet Scheduling: An Ireland-EU Mobility Case Study

Abstract

This work developed a simulation tool that incorporates both airline operations and aircraft specific capabilities when investigating the environmental and economic sustainability pathways for short haul aviation. A network of airports, centered around the island of Ireland and its connectivity to Europe, was created using the mathematics of multi-commodity flow networks and solved using mixed-integer linear programming. The model schedules a given fleet of aircraft to flights in the network such that passenger demand is met in the most environmentally and economically sustainable way. Three fleet composition cases are studied to investigate the impact hydrogen technology adoption has on the sustainability of an airline. The three cases vary the composition of the fleet with 0%, 25% and 50% of the fleet population being a liquid hydrogen fueled version of the B737-8200 MAX aircraft, with the balance of the population being the traditional B737-8200 MAX aircraft. The scheduling model is capable of completely scheduling an airline’s fleet and crucially, generating solutions that are influenced by the performance capabilities, both in-flight and with respect to ground operations, of the aircraft comprising its fleet. This important functionality within the model ensures that the solution offered by the optimization algorithm is intrinsically linked to and dependent upon both the airline’s operational attributes and the specific aircraft parameters. Airline sustainability was analyzed to determine the business case and environmental benefits of adopting varying compositions of hydrogen fueled aircraft by a European airline, to characterize the role of alternative fuels on a fleet-wide basis and to help inform and provide insight into the role of hydrogen technology on the route to net-zero. It was found that 8.77% of CO2 emissions could be eliminated with only three airports adopting hydrogen technology, with higher CO2 reductions achievable for increased numbers of hydrogen infrastructure at airports. Hydrogen aircraft offered significant sustainability gains but were prevented from universal adoption across the network of operations due to their higher associated operating costs therefore highlighting the imperative need for policy and legislation to incentivize the insertion of this technology within the sector.