When Southwest Airlines began service in the Twin Cities in 2009, the long-anticipated move was cheered by travelers hoping for additional flights and competition.

Nearly five years later, Southwest has drawn enough fans at Minneapolis-St. Paul International Airport to expand its nonstop schedule to eight cities. On the routes it serves, passenger counts have tended to increase and airfares have trended downward, a welcome effect at an airport that’s been criticized for few choices beyond Delta Air Lines — which, also five years ago, acquired locally based market-dominant Northwest Airlines.

“We’re meeting our expectations,” said Dan Landson, a spokesman for Dallas-based Southwest. “The last five years have been good for us.”

When Southwest started flying to markets such as St. Louis and Kansas City, data show the impact was immediate at MSP: higher passenger traffic and lower airfares on those routes.

What’s not as clear is whether the fabled “Southwest effect” has carried over more broadly at MSP. The effect is noticed regularly at airports that gain Southwest service: an increase in overall traffic, with the underlying assumption that lower airfares pull in more passengers.

While Southwest has brought additional competition to its nonstop routes here, airline observers say there’s something that’s packed more of a punch than the Southwest effect: the Great Recession. And the numbers at Minneapolis-St. Paul International back that up.

Annual passenger traffic at MSP peaked in 2005 at 37.6 million. Since then, it’s never been higher than 34 million and is on pace to hit about 33.7 million in 2013.

Both business and leisure traveler counts have been down at MSP since 2005, said Brian Peters, a business developer for the Metropolitan Airports Commission, which runs the Twin Cities airport. Peters’ job includes convincing new airlines to start offering service here.

“The biggest change has been that Delta has a smaller operation here than Northwest had at its peak time,” Peters said. “The industry’s a lot different today than it was in 2005. There are fewer flights, and more full flights.”

And in the bigger picture, Southwest still is a small player in the Twin Cities. For the full-year 2012, Delta and its affiliates carried 76.5 percent of the passengers at MSP, while Southwest and its subsidiary AirTran had 5.6 percent.

Chicago Connections

Across the nation, as Southwest has grown, it’s stopped fitting the profile of a low-cost carrier, said Michael Boyd, an airline industry analyst. The point-to-point flying model that Southwest used in its earlier days has started to look more like the hub-and-spoke system used by legacy airlines such as Delta.

“That’s a change they’ve had to make” for greater efficiency, Boyd said.

In Denver, about 45 percent of Southwest’s passenger traffic is catching connecting flights, he said. At Chicago’s Midway airport, it’s about 50 percent.

The routes to Chicago’s two airports are among the most heavily traveled out of MSP, and the airline competition for those routes is arguably as healthy as it’s ever been. All airlines included, there are about 45 departures per day out of MSP to O’Hare and Midway, Peters said.

Southwest began operations at Midway in 1985, and now, with AirTran, is the dominant carrier at Chicago’s smaller airport. The two carriers control 34 of the 43 gates at Midway and serve 60 nonstop destinations.

For Seneca Giese, a regional manager for Tesla Motors who is based in Chicago, the convenience of flying Southwest is key. He flies occasionally to visit Tesla’s service center in Eden Prairie.

“I live close to Midway (airport),” he said, “and my company takes care of the airfare. It tends to be pretty low as it is.”

London or Lubbock?

Southwest and other low-cost carriers are now actively pursuing business travelers like Giese, one more trend that industry observers say is blurring the distinctions between low-cost and network airlines.

Still, attracting business travelers away from large carriers like Delta remains a challenge, in part because the low-cost carriers don’t offer a big selection of international flights.

People flying for work “want to be on Delta so they can build up frequent flier miles and they can fly to London,” said Boyd, the airline industry analyst. “They don’t want to build up (Southwest) segments so they can fly to Lubbock.”

When Southwest started ramping up its service at MSP in 2008 and 2009, airfares already had dipped a little, mostly due to the recession, Peters said. Overall, “to say fares are down due to Southwest wouldn’t be accurate,” Peters said. But the increased competition from other low-fare carriers, including Sun Country, Frontier and the newest arrival, Florida-based Spirit Airlines, has offered ongoing competition on some popular routes.

On its nonstop routes where Southwest isn’t the only low-cost carrier, the airline’s effect on airfares isn’t as noticeable, Peters said. That includes Denver, which is served by Frontier Airlines, and Phoenix, which is served by Sun Country.

Home Depot or Dallas?

Back in 2009, Southwest announced its Chicago service with an airfare of $69 each way. Close to five years later, a round-trip to O’Hare or Midway still can be found for less than $150, and closer to $80 on Spirit, the rock-bottom a la carte-pricing airline, which started service at MSP’s smaller Humphrey Terminal in May. Spirit offers nonstop flights to nine cities, though several are seasonal destinations.

Spirit’s unique business model has proven to actually bring new passengers into airports, Boyd said. Prospective Spirit passengers might decide “that instead of going to Home Depot, we’ll go to Dallas,” Boyd said.

For 2014, airfares at MSP are expected to remain flat, according to a study released earlier this year by Carlson Wagonlit Travel. An anticipated increase in airfares for 2013 in the Twin Cities was tempered by a decline in demand for business flights and Delta Air Lines’ decision to add some capacity at the airport, the report said.

Southwest’s Landson wouldn’t say if more destinations are on tap for MSP. But the airline does monitor which city-pairs customers search online even if they don’t book the flight — data that can guide the selection of future nonstop destinations, he said.

Another possibility became clear earlier this month, after reports that Southwest would buy 22 landing slots at New York York’s LaGuardia Airport. The slots opened up after American Airlines was required to sell them to win government approval of its merger with US Airways Group.

Southwest service to New York would bring a new level of competition on the route, which already has low-cost carrier Sun Country offering flights to JFK International in New York.