European Air Transport Transformation: Network-Based Insights into Post-COVID and Restrictions-Induced Route Shifts

This dissertation examines the development of the European air transport network between 2019 and 2025 in the context of two major systemic disruptions: the COVID-19 pandemic and subsequent airspace restrictions affecting the region. Using flight data from the OpenSky network, the study applies network science methodology to analyze changes in the structure, connectivity, centrality of airports, and network resilience on quarterly and annual time scales. Directed weighted graphs were constructed for each period, and centrality measures were used to quantify the importance of airports and assess changes in the network hierarchy. PageRank was chosen because it captures indirect connectivity and is widely used for ranking in directed graphs. To study long-term dynamics, annual PageRank trajectories were clustered using the K-means method, which revealed four distinct behavioral patterns among European airports. Network resilience was assessed using percolation experiments simulating both targeted and random node and edge removal. The results show that COVID-19 caused a sharp structural collapse in 2020, followed by a gradual recovery and significant reorganization in 2022–2025. Traditional Western European transport hubs such as Frankfurt, Munich, and Amsterdam retained their influence but experienced relative decline. In contrast, several airports, such as Palma de Mallorca, Istanbul, Nice, Porto, and Krakow, have gained in importance, reflecting the rerouting of traffic flows and the rapid recovery of leisure and tourism-oriented routes. Percolation tests showed that the 2021 network was the most fragile, while the 2025 network demonstrated the greatest resilience, indicating increased redundancy and a more distributed hub structure. Overall, the European air transport network has not simply recovered to its pre-pandemic state; it has transformed into a more diversified, interconnected, and resilient system. The results indicate a gradual geographical rebalancing of European connectivity and provide a methodological framework for monitoring structural changes in complex transport networks.