Short answer, not as much as the pundits think. Delta has been competing successfully with Air Tran for a long time now. While Southwest is a much stronger company than Air Tran, the broohaha about their being some kind of low fare juggernaut is overrated if you ask me. Their costs are higher than Air Tran’s, and at a minimum I think this means that it’s not likely that they are going to swoop in and throw a bunch of trash airfares into the Atlanta market. Furthermore, most really informed travelers know that Southwest doesn’t always (if ever) offer the absolute lowest fare in any given market. What they do offer is reasonable fares, generous ticket change policies, and the ability to check up to 2 pieces of luggage included in the cost of your base fare.
Delta has a fairly loyal base of business customers in the Atlanta market, first class cabins, normal boarding, assigned seats, and the ability to fly you to many, many more cities on its global network than a combined Air Tran and Southwest. Delta will certainly need to be on its toes as it faces a much stronger competitor in its home town, a competitor with an almost mythical reputation for customer service. But in the end, I just can’t see this deal being the end of the world for Delta….yet. Opinions vary, and now you know mine.