Low-cost carrier AirTran had the best overall performance of the 16 largest U.S. carriers last year in an annual study of airline quality, knocking Hawaiian Airlines, the previous leader, into second place.

Regional carrier American Eagle ranked last in the study, which is based on Department of Transportation data.

Overall, airlines improved their performance last year. They lost fewer bags, bumpings due to overbooking were down and on-time arrivals were up. But travelers were still dissatisfied -- complaints to the Transportation Department about airline performance went up a whopping 28 percent in 2010, the study said.

Southwest Airlines maintained its ranking as the airline with the lowest consumer complaint rate, 0.27 per 100,000 passengers in 2010. Delta had the worst rate again, 2 per 100,000 passengers.

Details at aqr.aero.

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