The Southwest acquisition of AirTran signals major changes in airline service at Hartsfield-Jackson International Airport. Most of them are not what people are expecting.

Southwest is one of America's most ethical companies. Its success is because they really do like their customers, and it shows on every flight. From that perspective, Southwest is a great successor to AirTran.

However, Atlanta consumers are in for some surprises when Southwest launches service next month. First, there will be fewer flights.

Over 60 percent of all passengers on AirTran's Atlanta flights are connecting to or from other cities. But Southwest has announced that it will "unwind" that connecting operation, which means fewer passengers through Atlanta, and hence, fewer flights than AirTran is operating.

In fact, Southwest has indicated that it will operate 13 percent fewer flights at Atlanta than AirTran. Since connecting passengers represent the equivalent to fill about 100 of the current 180 AirTran flights, these reductions are likely just the first.

Fact: More than 25 of the cities to which AirTran now flies have less than 40 percent of the passengers made up of folks going to or from Atlanta. The other 60 percent are connections. Without these, Southwest will not be able to support those routes.

And there won't be much of a "Southwest effect" --- where a sudden reduction in fares will stimulate more traffic. AirTran has already achieved that in 24 of the top 25 routes from Atlanta.

Remember, Southwest's operating costs are higher than AirTran's. It's the added connecting passengers that support the high-flight frequencies. That means that if Southwest is only after Atlanta passengers, they absolutely will need to reduce flights from where AirTran is today. (To read a report on Southwest's merger effects on Atlanta, go to www.aviationplanning.com.)

As for Delta, they're not worried. In fact, they're probably smiling broadly.

The merger gives them a higher-cost competitor than AirTran, and one with a much more limited product. There's no advance seat selection on Southwest, and regardless of the hype, a lot of travelers prefer it. But, for a family of four, not knowing until they get on the plane whether they'll be sitting together is an issue --- one that they didn't always have with AirTran. Unlike AirTran, there are no business-class seats for passengers to upgrade to, either. And the Southwest strategy to not chase connecting passengers in Atlanta opens a huge new base of passengers for Delta.

Then we have the issue of operational systems.

Unlike AirTran, Southwest has work rules that restrict how it can handle flights at airports. AirTran can use outside vendors and part-time employees. This means a number of the routes that AirTran could fly --- not only at Atlanta, but elsewhere --- Southwest cannot. Example: Bloomington, Ill., was a successful market for AirTran. Southwest decided it couldn't make money there. Result: over 48 percent of Bloomington's traffic is at risk. That's a downside of this merger. Some communities are seeing air service reduced --- as Atlanta will.

There's no argument: Southwest is a fine company. But it's a very different airline than AirTran, and that means it will have a different operation at Atlanta, too. A smaller one. Our forecasts indicate passenger traffic through the airport will decline by about 6 percent as a result of this merger.

It's nothing personal. It's strictly business.

Michael Boyd is president of Boyd Group International, an aviation research and consulting firm in Evergreen, Colo.

Copyright 2012 The Atlanta Journal-Constitution