As the U.S. air travel market continues to splinter, airports must view air service differently, accepting that old metrics such as hub connectivity may not be the best way to evaluate a community’s service quality. 

That’s the thesis behind a new study from consultants Swelbar-Zhong that attempts to quantify air service quality at U.S. commercial airports. Each airport is evaluated on a set of variables, including the types of carriers that serve them, nonstop service routes, connecting routes, seats, and frequencies. Individual airport factors are weighted based on their importance—multiple frequencies are more important that total seats, for instance. 

The result, according to the firm, is an “airport accessibility index” (AAI) that gives airports a score that it can use to compare itself to peers—and paints a more complete picture than simple metrics such as total seats or enplanements.

“Not all airports are created equal,” Swelbar-Zhong chief industry analyst Bill Swelbar said. “Everybody’s portfolio of service is different. Everybody’s demand portfolio is different.”

Among the key variables is the AAI’s contention that air service can be segmented into four distinct categories: full-service network carriers, hybrid carriers such as Alaska Airlines and JetBlue Airways, ULCCs, and Southwest Airlines, which is large and distinctive enough to get its own category. 

Service to network carrier hubs has long been the yardstick of how well a community is connected. While still important, the growth in the other segments—notably ULCCs—is increasingly filling gaps created by mainline carrier schedule adjustments. 

“The importance of Southwest, hybrid carrier, and ULCC air service is significant, and vitally important to many,” the firm’s writeup on its initial AAI explains. “Connectivity is not the only attribute provided by commercial air service that should be considered by airports, their boards, and most of all their elected leaders, despite its inherent significance.”

The study is designed for airports to look at similar peers—small hubs comparing themselves to other small hubs, for instance. But some big-picture takeaways are evident from the aggregated data. Among them: hybrid and ULCC carriers have done the most to increase service quality within the U.S., followed by Southwest. The three majors—American Airlines, Delta Air Lines, and United Airlines—provided slightly less overall service quality in 2022 compared to 2019. 

Within the airport segments, small hubs have benefited the most, with an aggregate 27% increase in service quality, far outpacing large hubs (5.1%) and medium hubs (2.1%). 

“Nearly every air carrier sector found fertile ground to improve service at the small-hub airports,” the report said.

The picture is different at non-hubs, where service quality at the top 50—the only ones included in the study—fell 7.2%. Within that group, 28 airports saw their specific AAI score decrease compared to 2019.

“Our finding shines a klieg light on the fact that this group of airports—even the largest non-hub airports—will only continue to get smaller and may atrophy at a faster pace than expected,” the report said.