Integrated hub airport location and fleets planning for airline-alliance-oriented freight transport system

The rapid growth of e-commerce has led to a surge in air cargo demand. Rather than operating independently, airlines are increasingly collaborating to capture a larger market share. This study investigates the integrated hub airport location and fleet planning problem under the context of airline alliances to enhance sustainable urban freight transportation. Three optimization models are proposed in different airline cooperation modes: i) model INDHL-INDFP, where airlines independently determine hub airport locations and fleet planning, ii) model INTHL-INDFP, where airlines collaboratively decide hub airport locations while planning fleets individually based on their cargo demand, and iii) model INTHLFP, where airlines make integrated decisions on both hub locations and fleet planning. These models are applied to networks of varying scales, and their performance is compared. Results indicate that integrated decision-making within airline alliances effectively reduces total system costs, with cost-saving benefits becoming more pronounced as network size increases. Additionally, this approach aligns freighter capacity with cargo demand, enhancing system resilience to demand fluctuations. Sensitivity analysis further reveals that the optimal number of hub airports depends on network scale and varies under different airline cooperation strategies. Moreover, network size significantly influences the determination of the maximum number of flights connected to other hubs for a hub. This study provides valuable insights into optimizing airline cooperation strategies to improve efficiency and sustainability in air cargo transportation.