  Changes in air transport networks over time may be induced by competition
among carriers, changes in regulations on airline industry, and socioeconomic
events such as terrorist attacks and epidemic outbreaks. Such network changes
may reflect corporate strategies of each carrier. In the present study, we
propose a framework for analyzing evolution patterns in temporal networks in
discrete time from the viewpoint of recurrence. Recurrence implies that the
network structure returns to one relatively close to that in the past. We
applied the proposed methods to four major carriers in the US from 1987 to
2019. We found that the carriers were different in terms of the
autocorrelation, strength of periodicity, and changes in these quantities
across decades. We also found that the network structure of the individual
carriers abruptly changes from time to time. Such a network change reflects
changes in their operation at their hub airports rather than famous
socioeconomic events that look closely related to airline industry. The
proposed methods are expected to be useful for revealing, for example,
evolution of airline alliances and responses to natural disasters or infectious
diseases, as well as characterizing evolution of social, biological, and other
networks over time.
