Evolution characteristics of China’s international air transport network under impact of COVID-19

Under the global COVID-19 pandemic, the various international flight policies and the huge decline in international routes and passengers have had a significant impact on the structural characteristics of China’s international air transportation network. It is important to analyze the characteristics and evolution of China’s international air transportation network for airlines’ future international route recovery and resource allocation decisions. In this paper, the ${\rm{K}}{\text{-}}{\rm{Core}}$ algorithm is used to decompose China’s international air transportation network into different layers from 2019 to 2021. By analyzing the characteristics, level belonging, and transit passenger share of each node, the different layer functions were determined and the development trend of the network structure was concluded. In addition, the network was purposefully assaulted by eliminating nodes one at a time in accordance with their node relevance. The nodes were ranked and appraised by taking into account node degree, passenger flow, and the number of infected persons. Therefore, the evolution of network robustness was analyzed which is helpful to identify the key nodes in different periods. It demonstrates how the network structure and node functions have changed, some of which will be irreversible, as a result of internal and external factors such as decreased passenger numbers and international flight policies. The connectivity and dominant role of the core layer on the entire network are gradually weakened, the transfer function of the bridge layer is further strengthened, and the periphery layer will become the most promising recovery market. Airlines can consider establishing stronger connectivity with these nodes, which can not only maintain the normal operation of the network in case of emergencies but also rebuild key transit nodes during the network recovery period and improve passenger demand.