Delta Air Lines fell a notch in a closely-watched ranking of airlines based on customer satisfaction, although overall satisfaction with the industry improved.

Delta fell to the No. 5 spot in a ranking of "traditional network carriers" by J.D. Power and Associates in its 2011 North America Airline Satisfaction Study. Atlanta-based Delta came in behind Alaska, Air Canada, Continental and American, while edging out United and US Airways.

While airline surveys are numerous, the J.D. Power rank is important at Delta. The top customer service target in the company's annual goals, known as the "flight plan," is to earn the J.D. Power award. Instead Delta is instead falling further away from that goal, dropping from third in 2009 to fourth last year and fifth this year.

Among low-cost carriers, JetBlue Airways maintained its position in the No. 1 spot, followed by Dallas-based Southwest Airlines, which acquired AirTran Airways and plans to eventually fly to Atlanta as it folds AirTran's operations into its own.

AirTran was fourth out of five low-cost carriers.

Overall, customer satisfaction with airlines improved to 683 on a 1,000-point scale, up 10 points from last year, according to J.D. Power. Low-cost carriers have higher satisfaction ratings than network carriers, and the gap is widening.

Satisfaction in nearly all areas is improving expect for cost and fees, the study shows. "Additional fees for food, beverages, baggage, priority boarding and seat upgrades continue to weigh on satisfaction as carriers seek more ways to diversify and grow revenue," according to J.D. Power.

One area of improvement is satisfaction with automated check-in and reservations. Customers "appear more satisfied with the convenience and speed that technology has enabled," said Stuart Greif, J.D. Power's vice president and general manager of its global travel and hospitality practice, in a written statement.

The study is based on responses from more than 13,500 passengers who flew on a North America airline between July 2010 and April 2011.

Traditional network carriers

1. Alaska: 680

2. Air Canada: 678

3. Continental: 661

4. American: 656

5. Delta: 650

6. United: 640

7. US Airways: 625

Low-cost carriers:

1. JetBlue: 773

2. Southwest: 769

3. WestJet: 729

4. AirTran: 690

5. Frontier: 688