Higher fees, fewer bags and happier fliers? Customer satisfaction levels are on the rise for most airlines -- except Delta -- suggests a J.D. Power and Associates survey released Tuesday.

But the study's director said numbers don't tell the whole story in Delta Air Lines' case. For the first time since Delta absorbed Northwest in 2008, the annual study combined results for the two airlines.

"It's the tale of two Deltas," said Stuart Greif, J.D. Power's vice president of global travel. "They really did bring the standard performance of Northwest up."

The former Eagan-based airline scored poorly on the annual survey between 2007 and 2009, ranking eighth, seventh and sixth, consecutively. Delta, on the other hand, had remained near the top of the eight network airlines.

This year those scores were combined, although some flights flew under the Northwest banner until Feb. 1.

Delta received a rating of 640 out of a possible 1,000, two points below the average of its peers and one point below its 2009 score. This year's score ranked Delta fourth among seven traditional network airlines.

Alaska Airlines ranked first among traditional carriers, while JetBlue Airways topped the list of low-cost carriers and scored the highest rating overall.

Satisfaction with airlines in general moved up despite increasing ancillary costs and rising fares, the survey found. Greif said one reason could be that a drop in passengers meant less congestion and fewer delays.

"The impact on satisfaction overall was positive," Greif said. "Passengers, after a number of years of these fees, are starting to be more accepting of them as normal."

The J.D. Power satisfaction survey ranked more than 12,000 customer responses in seven areas: cost and fees; flight crew; in-flight services; aircraft; boarding/deplaning/baggage; check-in; and reservation.

During the past year, Greif said Delta had improved its in-flight services, booking options and travel packages. But customers cited its check-in process and loyalty program perks as areas that still lagged behind. Delta implemented a new program in April, a Delta spokeswoman said.

Greif said that if Northwest had been broken out as an airline, it would have scored 643, up from 614 a year earlier. The climb shows how Delta was able to apply the same standards across its brand, he said.

The owner of a Minneapolis-based travel website agreed.

"It vindicates Delta Air Lines," said Terry Trippler, owner of RulestoKnow.com. "People were expecting the merger to be a mess."

Delta placed considerably higher in the survey than in the 2010 Air Quality Rating released by the U.S. Department of Transportation in April. In that survey, Delta ranked 15th while Northwest was in fourth place.

But Trippler said more weight should be given to J.D. Power's survey, which he called the "Cadillac" of ratings. This year's survey results, he said, are a good sign for airlines and customers that the industry is starting to rebound.

Molly Young • 612-673-4376