U.S. air passenger service: a taxonomy of route networks, hub locations, and competition

In this paper, we analyze the service provided by the 13 largest U.S. passenger airlines to the 100 most populous U.S. metropolitan areas in 1989. We classify the route systems by their nature and geographical extent using a variety of measures based on route-level data. We then identify individual airline hub locations and derive and calculate several measures of the extent of competition both on individual routes and at the airports in our sample. The results show the wide diversity of route networks that existed in the airline industry in 1989--a phenomenon that may help to explain the failure of several major carriers since then.