Determinants of air cargo volumes within airport networks: Insights from an augmented gravity model with economic distance and geographic threshold effects

This study analyzed the determinants of air cargo volumes between airports using an augmented gravity model. Data from 115 airport pairs in China spanning 2009–2020 were utilized. The findings reveal that economic disparity significantly influences air cargo volumes, with greater economic differences between airports' host cities leading to reduced cargo flows. Geographic distance also plays a crucial role and exhibits a nonlinear effect. By extending the panel gravity model into a threshold regression model, this study finds that when the distance is less than 430 km, air cargo connectivity weakens as the distance increases. Beyond 430 km, however, geographic distance positively impacts air cargo volumes, indicating that air cargo frequency increases with longer distances. Population size in airport host cities affects cargo volumes, with departure city populations having a stronger influence. Additionally, airport-specific factors such as available tonnage, flight schedules, and regular shift load factors are significant determinants, with the regular shift load factor being particularly impactful. By incorporating time-varying economic distances and geographic threshold effects, this study improves upon the traditional gravity model, offering a more nuanced approach for analyzing airport cargo flows. The findings provide valuable insights for policymakers, enabling them to better understand the factors influencing air cargo volumes and implement effective strategies to foster sustainable growth in the air cargo industry.