American Vs. Delta Vs. United: The US’s Top 10 Fortress Hubs Unveiled

The concept of fortress hubs is straightforward. While definitions vary, it is where one airline has at least 70% of an airport’s flights, which may or may not be achieved by deploying many smaller-gauge regional jets. Of course, dominance will rise further when a carrier’s alliance members and partners (interline, codeshare, joint venture, etc.) are added.