An airport hub is a central airport where an airline concentrates its operations, routing passengers from smaller cities through one location so they can connect to flights heading to their final destinations. Rather than flying directly between every pair of cities, airlines funnel travelers through these hubs, creating a network that looks like a wheel with spokes radiating outward. This design lets airlines serve far more destinations with far fewer flights than a direct-connection model would require.
How the Hub-and-Spoke System Works
The logic is straightforward. Imagine five cities that all need air service to one another. Connecting every city directly to every other city would require ten separate routes. But if one airport serves as the hub, all five cities can be linked with just four routes, because every passenger simply passes through that central point. The trade-off is that most travelers have to make a stop along the way, but the airline operates with significantly fewer planes, crews, and gates.
Airlines collect passengers from smaller “spoke” cities on feeder flights, bring them into the hub, and then send them out again on flights to their destinations. The entire process is built around tight transfer windows. Passengers typically land and connect to their next flight within 40 to 50 minutes. To make this work, airlines don’t spread their flights evenly across the day. Instead, they schedule them in clusters called “banks” or “waves,” where a large group of planes arrives nearly simultaneously, passengers swap between gates, and then a wave of departures pushes out shortly after. A major hub might cycle through two to four of these banks in a single day.
Designing these banks is a complex optimization problem. Airlines have to balance arrival and departure slots at congested airports, minimize connection times so passengers aren’t stranded for hours, and avoid overwhelming terminal capacity during peak windows. The goal is making as many city-pair connections as possible within the shortest layover.
Hub Airports vs. Point-to-Point
The alternative to the hub model is point-to-point service, where airlines fly directly between cities without funneling anyone through a central airport. Budget carriers like Southwest and Ryanair lean heavily on this approach. It’s simpler for the passenger (no connections, shorter travel times) but harder for an airline to scale, because offering nonstop flights between dozens of cities requires a huge number of routes.
Hub-and-spoke networks give airlines economies of scale. They can fill larger planes on popular hub routes, concentrate their maintenance and crew bases in one place, and offer service to small cities that could never support a direct flight to, say, London or Tokyo. The downside lands squarely on the traveler: layovers, the risk of missed connections, and often higher fares.
The Hub Premium on Airfares
Flying out of a hub airport tends to cost more, not less. Airlines that dominate a hub can charge what researchers call a “hub premium” because they face limited competition on many routes. One widely cited study found that tickets originating from a hub cost about 8 percent more than comparable tickets from non-hub airports. Flights into a hub carry a smaller but still measurable premium of around 6.4 percent. This happens because a dominant airline at its own hub controls so many gates and slots that competitors struggle to offer alternatives, giving the hub carrier pricing power.
Which Airlines Dominate Which Hubs
Most major airlines anchor their networks around one or two primary hubs where they control a large share of all flights. In the United States, Delta Air Lines operates 79 percent of flights at Atlanta’s Hartsfield-Jackson, making it one of the most dominated hubs in the world. American Airlines controls 85 percent of flights at Dallas/Fort Worth. United Airlines splits its hub operations between Chicago O’Hare (49 percent of flights) and Houston’s George Bush Intercontinental (80 percent).
Internationally, the pattern is similar. Lufthansa holds 56 percent of flights at Frankfurt and 54 percent at Munich. Emirates operates 38 percent of flights at Dubai International, a lower share that reflects the airport’s role as a global crossroads with many competing carriers. These percentages matter because they directly influence how much competition exists on routes in and out of those cities.
Some hubs are sometimes called “fortress hubs,” an informal term for airports where one airline’s dominance is so complete that breaking in as a competitor is nearly impossible. Atlanta for Delta and Dallas/Fort Worth for American are textbook examples.
How the FAA Classifies Hub Airports
The Federal Aviation Administration uses a separate, more technical definition of “hub” based purely on passenger volume, not on whether an airline uses the airport as a connecting point. Under the FAA system, any commercial airport handling more than 10,000 passengers per year is classified as a primary airport, and these are then sorted into tiers. A large hub receives 1 percent or more of all U.S. passenger boardings in a given year. A medium hub handles 0.25 to 1 percent. A small hub falls between 0.05 and 0.25 percent. Airports below 0.05 percent but above 10,000 boardings are labeled nonhub primaries.
This classification determines federal funding levels and planning requirements, but it doesn’t necessarily align with the airline industry’s use of the word “hub.” An airport can be an FAA-designated large hub without serving as a connecting hub for any particular airline, and a smaller airport could function as a regional connecting hub without qualifying as a large hub by FAA standards.
Economic Impact on Surrounding Communities
Hub status transforms a region’s economy. Airlines bring not just flights but maintenance facilities, corporate offices, catering operations, and cargo logistics. The jobs and spending ripple outward into hotels, restaurants, rental car agencies, and local businesses that serve travelers and airport employees. Even a mid-sized airport like Dane County Regional in Wisconsin generated $2.6 billion in total economic impact in 2024 and supported more than 10,000 jobs. Direct airport operations alone accounted for $1.7 billion in business sales and over 5,500 jobs. For every dollar of direct business the airport produced, an additional 52 cents circulated through the surrounding economy.
For major hubs handling tens of millions more passengers, the numbers scale dramatically. This is why cities compete fiercely to attract and retain hub operations. Losing hub status, as cities like St. Louis and Pittsburgh experienced when airlines restructured, can mean the loss of thousands of jobs and a sharp decline in nonstop destinations, making the region less attractive to businesses considering where to locate.