The set up varies but the punch line stays the same – you can’t get there from here.

It’s such an old joke, few can remember if it was ever funny. But Maine’s lack of competition among discount air carriers has made it less of joke than an accurate reflection of reality.

That should change with the news that Southwest Airlines, the nation’s biggest domestic air carrier, has purchased a smaller rival, Air-Tran Airways, which includes stops in Portland among its routes. The deal would add Portland to Southwest’s considerably larger network, making it possible for Maine people to affordably reach a much wider selection of destinations, and let people in those place find a lower-cost way to get here.

Combined with a near doubling of the jetport’s capacity in an ongoing construction project this promises to increase the number of flights to and from Portland, creating more competition among carriers, if not actually lowering prices, at least slowing down their increases.

For a state that depends on tourism, Southwest’s foothold in Maine is great news. For people who recruit businesses to the state, an expanded jetport with more discount flights is a good selling point.

For the rest of us, who love Maine but wouldn’t mind leaving it once and awhile, better access to the nation’s airports at affordable rates will be a pleasant addition.

This will change the set-up so drastically we may have to rewrite the punch line. You can get there from here, and they can get here from there, too.