WASHINGTON — Airlines carried fewer people last year, but did a better job for those who did fly.

The rates of lost bags, late arrivals, passengers bumped from overbooked flights and consumer complaints all declined, private researchers say in their annual study of airline quality, based on government statistics.

While the industry had its best overall performance in the ratings in four years, the picture was not entirely rosy.

High fuel costs and a poor economy led many airlines to reduce schedules, raise ticket prices, jettison frills and put in place fees for everything from luggage to pillows.

Still, consumer complaints for the 17 airlines included in the study dipped from 1.42 per 100,000 passengers in 2007 to 1.15 in 2008. Southwest Airlines had the best rate, 0.25 complaints per 100,000 passengers; US Airways had the worst, 2.25.

The average on-time performance last year was 3 percentage points better than the year before, yet nearly one-quarter of all flights were late. The study being released today said only three airlines had better than an 80 percent on-time rate: Hawaiian Airlines, 90 percent; Southwest, 80.5 percent; and US Airways, 80.1 percent.

The study, compiled annually since 1991, is based on Transportation Department statistics for airlines that carry at least 1 percent of the passengers who flew domestically last year. The research is sponsored by the Aviation Institute at the University of Nebraska at Omaha and by Wichita State University in Kansas.

An overall ranking of the 17 airlines based on their combined performance in four categories was to be released today.