CHICAGO – Passengers may grumble about hidden fees and lugging bags onto aircraft, but their satisfaction with airline travel improved noticeably over the past year, a new survey suggests.

After three consecutive years of declines, overall customer satisfaction with North American carriers rose by about 15 points on a 1,000-point scale, and 10 of 12 airlines studied improved their scores from 2009 levels, according to the study released last week by J.D. Power and Associates.

Alaska and Continental airlines earned top marks from consumers among network carriers, while JetBlue Airways and Southwest Airlines scored best among low-cost carriers.

Two traditional carriers that have struggled in recent years saw the biggest gains in satisfaction among all airlines after they made concerted efforts to bolster operations and boost on-time departures: United Airlines’ score improved 26 points, while American Airlines saw a 24-point jump from the 2009 study conducted by the California-based research firm.

But it is too early to tell whether this marks a turnaround for an industry rife with poor service or whether it is a short-term blip, experts cautioned. Rising airfares, full planes and the pending merger of United and Continental all could have negative repercussions for passengers.

“It’s positive movement, but not just yet a positive story,” said Stuart Greif, vice president with J.D. Power’s global travel practice.

Airline scores remained well below 2006 levels, when the research firm best known for its study of automobile quality first started taking a closer look at carriers, Greif said. Airlines still receive lower customer approval ratings than the insurance industry and barely score above phone companies.

The economic storm that left the airline industry in crisis last year also made flying more pleasant for passengers, according to the latest study, which measured consumers’ views of everything from travel costs to aircraft cleanliness between April 2009 and April 2010.