Alternative pair in the airport network

This paper reveals the existence of “alternative pair” in the airport network. The alternative pair is defined as a pair of airports that, if one of them is closed, the other one can take over part of its traffic load. We find these pairs of airports important as the network performance will not be affected largely if only one airport is disrupted, while simultaneous closure of both airports in an alternative pair will worsen the network performance significantly, as no other airports can accommodate their load. A method is provided to identify the alternative pairs in an airport network and quantify the “alternative strength” between them. The alternative relations between different airport pairs are visualized using the “alternative graph”. By setting different thresholds of alternative strength, the alternative graph exhibits various patterns. The proposed method is applied to two domestic airport networks to obtain some managerial insights. It is found that airport networks are usually robust to the disruption of a single airport, but vulnerable to the simultaneous disruption of an alternative pair; furthermore, the two airports in an alternative pair may not be geographically close to each other in some airport networks.