If you've ever flown from airports such as Stansted, Dubai or Dallas Fort Worth, you'll have noticed that they appear all but dominated by one airline. Those airports are called Fortress Hubs, although they don't necessarily need to be hubs for an airline (some only provide point-to-point connections). But what defines a Fortress Hub? Counting the variety of aircraft liveries on the tarmac is not a very scientific method of determining such airports, so we used Flightera's database instead to get more insights in where those hubs are.
For this article, I looked at flights in November 2017. While flight patterns vary over the year, the composition of airlines often remains relatively stable and extending the sample size to include more months didn't change results. For an airline it's easy to dominate a small airfield so I only included airports with at least 200 departures per day. This number is somehow arbitrary but filters out all regional airports. I used the number of flight movements to measure concentration. One could argue that seat capacity is a more suitable indicator but as airport capacity is often restricted by the number of flights, and slots are distributed per flight, this seemed the better measure to use.
Throwing all flights together and ranking them by the number of flights result in the first chart seen below. Somewhat surprisingly, Middle Eastern Hubs are much less prevalent than initially thought, whereas US airports dominate the ranking. Of the top 15 airports, all but four are in the US. With Doha, only one Middle Eastern Hub made it into the ranking. Europe is represented with Moscow, Istanbul Ataturk (the airport is on the European side of the city) and Stansted, and there is no Asian airport on the list.
Just looking at US airports on the list, hubs I had expected to top the list (e.g. Atlanta, Dallas Fort Worth) are below the 80% mark. Charlotte tops the ranking as an American Airlines hub with a strategically good location (connecting East Coast and European flights) but serving a comparably small city. Charlotte Airport counted 45 million passengers last year for a metro area of just under 2.5 million people. The next ones on the list, however, are a different phenomenon. Both Chicago Midway and Dallas Love Field are secondary airports served by a low-cost carrier (Southwest in both cases).
What does that mean for passengers? In hubs such as Moscow, Doha or Istanbul, airlines depend on the airport and vice versa. But as soon as airlines dominate more than one airport, this power shifts. The second chart ranks airlines by the number of airports they dominate. Four out of the top five airlines are from the United States, with Southwest topping the list at six airports.
This can be both a result and cause for higher ticket prices in the US compared to Europe. As few airlines dominate the large US market this results in a higher airport concentration. But once airlines dominate an airport, they can prevent other airlines from serving the airport (via predatory pricing, slot restrictions and lobbying), creating a less efficient market.
This was just a start and there's much more to explore on the symbiosis of airlines and airports. If you want to compare other airports, we've added statistics on top airlines to the pages of each airport.
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