The multi-year shakeout that is reshaping U.S. airline networks is nearly complete, but smaller airports are suffering until the bitter end as carriers continue their shift toward strategies that emphasize bigger, more lucrative markets, a Moody’s analysis concludes.

“We think that the major shifts in the industry are nearing an end,” Moody’s notes in a recently released commentary on the U.S. airport sector, pointing to schedules after October’s expiration of the Wright Amendment and the fallout from the American-US Airways and Southwest-AirTran mergers as three of the recent dominos that have fallen.

Capacity discipline, combined with a push by majors to eliminate 50-seat regional jet flying in the face of rising fuel prices, has been pulling flights out of smaller airports for the better part of a decade. Large hubs captured 56.5% percent of all operations in 2013, the sixth straight year they gained share. In 2003, large hubs had 50.4% of all operations.

While upgauging is preserving capacity at some smaller airports, many are losing both operations and capacity. Southwest Airlines has trimmed or eliminated service in several markets, including Jackson, Mississippi, Key West, Florida, and Newport News, Virginia, as it shifts its schedule to accommodate new opportunities at Ronald Reagan Washington National Airport, New York LaGuardia Airport, and—after the Wright Amendment expires on October 13—Dallas Love Field.

Once the poster carrier for using secondary airports, these days Southwest acts more like the carrier that enplanes the most U.S. domestic passengers. In 22 of the 45 markets the carrier serves that are not large or medium hubs, current flight levels are at least 40% below all-time peak levels, Moody’s calculates. In 20 of them, the service dip has been 20% in the last two years alone.

New opportunities are not helping spread the wealth. Southwest’s Love Field schedule, set to be in place by early November, includes no nonstop service to small hubs, Moody’s reports. The carrier’s new service at Reagan includes service to one small hub: Akron, Ohio.

Competition among hubs and nearby alternatives is tilting in favor of the larger airports. In the greater Boston market, Boston Logan had 69% of the domestic enplanements generated by it and its closest rivals, Manchester Boston Regional and Providence’s T.F. Green airport. In March 2014, Logan’s share was up to 81%.

A similar evolution in the Los Angeles area has seen Los Angeles International boost its share of domestic enplanements from 62% to 70% from March 2004 to March 2014, compared to Bob Hope, Long Beach, Ontario, and Orange County.

“We expect competitive pressures on airports within driving distance to large hubs to continue,” Moody’s says. “The periphery airports face a host of realities in the new airline operating world that will influence passengers to choose to fly from the large hubs.”

Among the new realities: more nonstop options from the large hubs, and more chances to avoid regional jets, Moody’s notes. The roll-out of expedited security screening also gives some airports an advantage. TSA’s Pre-Check program is now available at 118 airports.

On the carrier side, a decline in regional jet operations has meant less-crowded large hubs, freeing up landing slots and gate space for larger equipment.