The COVID-19 pandemic has had a significant impact on the connectivity of the worldwide air transport network, and the accessibility of the network has been largely reduced. To study the variation in the external connectivity of Mainland China's air transport network under the influence of COVID-19, an evaluation metric named Weighted Domestic-Foreign Efficiency (WDFE) is proposed, and different link deletion principles are used to model the characteristics at different stages of the COVID-19 outbreak. It is found that in the early stage of the outbreak, Mainland China's WDFE dropped by nearly 39.8% compared to normal periods due to the entry restrictions adopted by many countries. The entry ban has a larger impact on Mainland China's external connectivity than the suspension of direct flights does, and the impact of these two restrictions is significantly different in various countries. In addition, some countries having no direct flights with Mainland China will also have a considerable impact on Mainland China's external connectivity if they take entry measures. In the mid-late period of the outbreak, the reduction of global flight connections has no major impact on Mainland China's external connectivity. The alternative relationship between Mainland China's external connections has dramatically improved the robustness of Mainland China's air transport network.
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