This paper studies the vulnerability of the worldwide air transportation network (WATN) during a global catastrophe such as COVID-19. Considering the WATN as a weighted network, many airport connections could be completely or partially disrupted during such extreme events. However, it is found that existing weighted metrics cannot reflect the impact of connection capacity reduction on network connectivity. Therein, this work proposes a novel network efficiency metric termed as layered weighted network efficiency (LWNE) metric to measure the connectivity of the air transportation networks (ATNs) and study their vulnerability in response to different levels of disruptions, including airport level, country level, and global level. The most critical airport connections and their impact on network connectivity are identified. It is found that the critical connections are mostly between so-called bridge airports but not core airports in the WATN. By examining the impact of partial link disruptions, it is found that some connections mainly serve local travel demand and are very robust to partial disruptions, while the others connecting global hubs are sensitive to partial disruptions. Further, the WATN is robust to the individual disconnection of most countries; however, it is vulnerable to the simultaneous disconnection of countries that serve international transfers. Interestingly, the WATN is insensitive to the disconnection between any two countries, even those with sizeable domestic ATNs. Concerning global disconnections, as long as all the international connections hold 10% of their original flights, the WATN can still expect 40% of its pre-disruption performance. This paper deepens the understanding of ATNs under extreme events and provides a method for studying transportation networks’ vulnerability facing global disruptions.

本文研究了全球航空运输网络 (WATN) 在全球灾难（如 COVID-19）期间的脆弱性。将 WATN 视为加权网络，在此类极端事件期间，许多机场连接可能会完全或部分中断。然而，发现现有的加权指标无法反映连接容量减少对网络连通性的影响。其中，这项工作提出了一种称为分层加权网络效率 (LWNE) 指标的新型网络效率指标，用于衡量航空运输网络 (ATN) 的连通性，并研究它们在应对不同程度的中断时的脆弱性，包括机场层面、国家层面, 和全球水平。确定了最关键的机场连接及其对网络连接的影响。结果发现，关键连接主要位于所谓的桥梁机场之间，而不是 WATN 中的核心机场之间。通过检查部分链路中断的影响，发现一些连接主要服务于本地旅行需求并且对部分中断非常稳健，而其他连接全球枢纽的连接对部分中断很敏感。此外，WATN 对大多数国家的个别断开连接具有鲁棒性；然而，它很容易受到为国际转移提供服务的国家同时断开连接的影响。有趣的是，WATN 对任何两个国家之间的断开都不敏感，即使是那些拥有相当大的国内 ATN 的国家。关于全球中断，只要所有国际连接保持其原始航班的 10%，WATN 仍可预期其中断前性能的 40%。