Why this sudden surge in popularity? So-called secondary airports are offering more flights and expanded, improved services. Last year, San Jose International remodeled the food courts in its two terminals and introduced higher-quality vendors, including a Gordon Biersch Brewery and the first Expedia.com Internet Café, where passengers can hook up their laptops for free. This spring, Chicago Midway opened a new terminal, and Oakland International is building 12 new gates.

Discount airlines, such as Southwest and America West, have long understood the appeal of secondary airports and preferred them to the sprawling hubs dominated by the major airlines. Southwest looks for airports where passengers "can have a convenient drive to the airport and where there will be enough parking," says spokeswoman Kristin Nelson. Five of the top 10 airports that Southwest serves are considered alternate airports: Chicago Midway, Oakland, Houston Hobby, Dallas Love Field, and Baltimore/Washington.

This summer, discount carrier JetBlue chose Long Beach Airport, just 20 miles south of LAX, to be its second hub (New York's Kennedy is its first). "At Long Beach, you can park for as little as $3 a day," says JetBlue CEO David Neeleman. "And it takes about a minute to get from your car to check-in at the landmark art deco terminal." JetBlue started twice-daily service between Long Beach and JFK this summer, with fares as low as $129 each way. The airline plans to offer 27 daily departures from Long Beach to as many as 22 cities within two years.

Bigger airlines are taking note. Continental flies nonstop from Newark, N.J., to Oakland and John Wayne International in Orange County, Calif. And American flies from its Dallas/Fort Worth hub to Long Beach.

What these alternate airports don't offer are hundreds of connecting flights. San Francisco has some 650 departures daily on 56 carriers, but Oakland offers only 194 daily departures on 12 carriers and San Jose, 232 daily departures on 15 carriers. Travelers who miss a flight at a secondary airport are likely to face a longer wait to catch the next plane.

Inevitably, as secondary airports become more popular, they are encountering some of the same problems that afflict their larger neighbors. Says Steve Grossman, director of aviation for Oakland International: "Since March, our on-airport lots have routinely filled, even on nonholiday weekends." The parking rates at Oakland went up this summer, and a new multilevel parking lot is slated to open in 2004.

Today's small airports may be tomorrow's big. Enjoy them while they last.