JetBlueand Alaska Airlines continued their stranglehold atop the annual J.D. Power customer service satisfaction survey of North American carriers. Those airlines also had the highest customer satisfaction ratings for their frequent-flier programs, according to the 2015 J.D. Power survey released Wednesday.

Overall, passengers' happiness with service on U.S. and Canadian airlines continued to rise, according to the J.D. Power survey. The industry's satisfaction score climbed to an average of 717 on a 1,000-point scale — a 5-point jump from the record-high in 2014. (Scroll down for a full list of the airline ratings)

The uptick in the average score was driven mostly by gains in fliers' satisfaction with airline flight crews and with in-flight services.

"Many airlines realize that they are not in a commodity business and that hospitality and service go a long way in differentiating them from the other airlines," Rick Garlick, global travel and hospitality practice lead at J.D. Power, says in a statement accompanying the 2015 survey results. "Hospitality and service impact loyalty and return on investment with a high percentage of loyal passengers who are better advocates for the airline."

Passengers also reported higher satisfaction with airline "costs and fees," likely indicating the customers have become desensitized to paying more for perks that used to be free.

The survey also found that passengers who picked an airline based on customer-service reputation rather than price reported a higher satisfaction score. Those passengers also were more forgiving of their carrier for late flights and other operational disruptions.

"When the airline provides good service, passengers are generally less critical when there is a departure delay or a late arrival," Garlick says.

An Alaska Airlines jet at Seattle-TacomaInternationalAirport on June 11, 2009,(Photo: David Zalubowski, AP)

Results of the new J.D. Power survey -- conducted between April 2014 and March 2015 -- are tabulated from the responses of 11,354 passengers who flew on a major North American airline between March 2014 and March 2015.

Satisfaction scores are drawn from airlines' performances in seven categories (in order of importance to the survey): cost and fees; in-flight services; boarding, deplaning and baggage; flight crew; aircraft; check-in; and reservations.

The J.D. Power ratings come afteranother annual airline rating found that airline service declined slightlyin 2014 from a year earlier. That study -- the Airline Quality Rating (AQR) report that's a joint project of Wichita State and the Arizona campus ofEmbry-Riddle Aeronautical University--tabbed Virgin America as the top U.S. carrierfor a third year in a row.

In the J.D. Power survey's individual airline ratings, JetBlue earned the top overall mark with 801 points on the 1,000-point scale. That gave JetBlue the top score both in its "Low-Cost Carrier" category and among all carriers surveyed. JetBlue's finish in 2015 marks the 11th-consecutive year that it has earned the top overall score in the J.D. Power North American Satisfaction Study.

Southwest had the second-highest score among low-cost carriers, earning 781 points on the 1,000-point score. With 659 points,Frontier Airlinesfinished last out of the five low-cost carriers in the survey.

Alaska Airlines garnered the highest score (719) in the category for "Traditional Carriers," giving it J.D. Power's top score in the category for the eighth year in a row.

Alaska Air bested second-place finisherDelta Air Linesby 10 points.United Airlinesfinished last out of the six "traditional" carriers with a score of 665.

Frequent-flier programs

Alaska Airlines' Mileage Plan program again received the highest overall customer satisfaction score among North American frequent-flier programs in 2015. It's the second year the J.D. Power has included loyalty programs in its ratings.

Alaska Airlines scored 759 points in the survey, edging out second-place JetBlue by a single point.

Loyalty program satisfaction scores are drawn from airlines' performances in six categories (in order of importance to the survey): ease of redeeming points or miles; reward program terms; account maintenance and management; ease of earning points or miles; variety of benefits available; and customer service.

Alaska Airlines has long been lauded by frequent-flier critics for its broad Mileage Plan program, which allows membersto earn and redeem miles with a dozen airline partnersthat span multiple frequent-flier alliances.

US Airways (670) and Delta (675) had the lowest satisfaction ratings of the seven programs included in the J.D. Power study. US Airways is in the the process of merging withAmerican Airlines.Its frequent-flier program was folded into American's AAdvantage programearlier this spring.

As for Delta,it has been slammed by frequent-flier criticsduring the past two yearsfor a series of unpopular changesto its SkyMiles programs. In particular, critics point to Delta's decision to stop publishing an award chart for its frequent-flier members.

At best, the movemakes it more difficult for Delta's frequent-fliersto figure out what the lowest mileage requirement should be for free flights to Delta's various global destinations. At the worst,critics sayit makes it easier for Delta to stealthily raise the number of miles its frequent-fliers must redeem for those free tickets.

Scroll down for the full results of the 2015 J.D. Power airline survey results.

2015 AIRLINE RATINGS

J.D. Power 2015 North America Airline Satisfaction Study

Traditional carriers

1. Alaska Airlines (719 points on a 1,000-point scale)

2. Delta Air Lines (709)

3. American Airlines (700)

Average score for "traditional" segment (691)

4. Air Canada (683)

5. US Airways (668)

6. United Airlines (665)

Low-cost carriers

1. JetBlue (801 points on a 1,000-point scale)

2.Southwest Airlines(781)

Average score for low-cost segment (766)

3. WestJet (715)

4.AirTran Airways(702)

5. Frontier Airlines (659)

2015 FREQUENT-FLIER RATINGS

J.D. Power 2015 Airline Loyalty/Rewards Program Satisfaction Report

1.Alaska Airlines Mileage Plan(759 points on a 1,000-point scale)

2. JetBlue TrueBlue (758)

3. Southwest Airlines Rapid Rewards (743)

Industry average (705)

4. American Airlines AAdvantage (700)

5. United Airlines MileagePlus (697)

6. Delta Air Lines SkyMiles (675)

7. US AirwaysDividend Miles(670)