Traffic distribution in low-cost and full-service carrier networks in the US air transportation market

After deregulation in the US in 1978, air carrier networks were increasingly focused around a small number of hubs. These ‘hub-and-spoke’ (HS) networks were the predominant form of network organisation of large carriers as well as smaller regional and commuter carriers. The passenger carrier networks typically consisted of between three and seven hubs, while the air freight carrier networks were typically focused around one or two hubs. A variety of measures of the traffic distribution in carriers’ networks have been presented in the economics and regional science literature. These measures are reviewed and compared for a sample of US major carriers for the period 1969–99. The HS network structure requires a concentration of traffic in both space and time. The summary measures presented focus on measuring the spatial concentration at discrete locations in the networks.