Over the years, price-conscious air travelers in Atlanta have come to realize that they can sometimes fly cheaper if they're willing to commute to Birmingham and fly from there, particularly on Southwest Airlines. Meanwhile, some Birmingham residents determined that they could do better by flying from Atlanta's Hartsfield-Jackson International Airport.

Mark and Libby McConville of Birmingham figured it out a long time ago, and for 24 years they have made their livelihood by ferrying those travelers back and forth via their bus shuttle service, Airport Express. That also allowed commuters to avoid the hassle of driving and the cost of parking.

Now, though, the future of their company is up in the air. When Southwest announced plans to acquire AirTran Airways, the need for Atlantans to fly from Birmingham, at least, seemed certain to be reduced, since Southwest would be flying from Hartsfield.

Meanwhile, Birmingham residents who wanted to fly from Atlanta because it offers more airlines and destinations, could just get on Southwest and fly at low cost to Hartsfield instead of paying $59 for the 21/2-hour, 150-mile one-way trip on Airport Express.

"We're scared," Libby McConville  said. "We don't know how the future's going to end up."

The McConvilles operate three round trips daily and two on weekend days. They have three vans that use compressed natural gas to save money. The service, Libby McConville said, "has basically always been a marginal business," with the 10-person capacity vans rarely full.

Looking ahead, the McConvilles hope to attract customers commuting for nonflying reasons, such as entertainment events, schooling or family reunions.

Larry Forest of Birmingham has been a frequent user of the service the past couple of years to fly from Atlanta to Bloomington, Ill., where he works as an independent information technology contractor.

Forest isn't sure yet how much his use of the shuttle will be affected, but he said he talks to other riders and "there definitely will be a reduction in their business."

The McConvilles, who have weathered the vagaries of air travel caused by events ranging from the Sept. 11 terrorist attacks to the recession, are looking ahead.

Said Libby McConville, "Part of being in business is learning to reinvent yourself."