A note on optimal airline networks under airport congestion

•Airport congestion is a severe economic problem.•We examine optimal airline networks under airport congestion.•Airlines exhibit a preference for hub-and-spoke (HS) configurations.•Airlines may be inefficiently biased towards HS networks.•We recommend regulatory tools like congestion pricing or slot constraints.

We extend the monopoly case without congestion in Brueckner (2004) by examining network choice in a duopoly where airport congestion can occur. Airlines prefer hub-and-spoke configurations, even if this implies higher congestion costs. Airlines may be inefficiently biased towards hub-and-spoke networks.