The others
Although few other main airports are as overused as those in the giant cities, alternative airports have been developed at several other big metro areas. Most provide only limited service. And, in several cases, the primary purpose of the alternative airports is not so much to relieve congestion at the prime fields as it is to entice airlines by offering lower costs.
Orlando
Some flights—especially foreign charters and some low-fare domestic services—use Orlando Sanford International Airport, because of lower costs, not convenience.
Phoenix
The main airport, Phoenix Sky Harbor, is promoting strong growth at Phoenix-Mesa Gateway Airport, Mesa, formerly Williams Air Force Base.
St Louis
MidAmerica St. Louis Airport, Mascouta, Illinois, is one of those "build it and they won't come" ventures. Airline service has been on-and-off; currently, it's limited to Allegiant.
San Francisco
Travelers to Marin County communities can avoid congested bridge traffic to/from San Francisco, Oakland, or San Jose by flying to Charles Schultz Sonoma County Airport, Santa Rosa, from Seattle or Los Angeles. Would probably warrant additional service, absent local opposition to most growth.
Allegiant and Skybus
Two low-fare lines specialize in serving underutilized airports, including some big-city alternative fields.
- Allegiant uses Bellingham (Seattle), Gulfport/Biloxi (New Orleans), Mid-America (St Louis), Rockford (Chicago), and Santa Monica (Los Angeles) for its less-than-daily nonstops to a few prime domestic vacation centers. It provides similar services from more than two dozen smaller cities around the U.S. that have either no scheduled service at all or services limited to short-haul feeder flights.
- Skybus uses Bellingham, Chicopee, Massachusetts (Hartford); Gulfport/Biloxi; Portsmouth (Boston); Punta Gorda, Florida (Ft Myers); and St. Augustine, Florida (Daytona Beach/Jacksonville) for its very cheap flights to/from Columbus. In many cases, those underused airports subsidize Skybus service.

