DALLAS -- Airlines are falling behind schedule more often and mishandling more bags, but customers aren't making a federal case out of it.
Academics who study the airline industry say that consumer complaints to the government dropped 15 percent last year after spiking in 2012.
The researchers will detail their conclusions in a report Monday. Among their findings:
-- Chicago-based United Airlines climbed out of last place in the rate of customer complaints.
-- American Airlines did better at staying on schedule last year than it did in 2012, when it accused pilots of a work slowdown.
-- Most of the worst grades -- from late flights and lost bags to bumping passengers off planes -- were earned by smaller regional airlines.
Researchers at Wichita State University and Embry-Riddle Aeronautical University compiled the report on airline quality from figures that the 15 largest airlines must report each month to the U.S. Department of Transportation. They graded the airlines on four categories:
ON-TIME PERFORMANCE: Airlines operated 78.4 percent of their flights on time in 2013, down from 81.8 percent in 2012. Best: Hawaiian Airlines; worst: American Eagle.
BAG HANDLING: The rate of lost, stolen or delayed bags rose 5 percent. Best: Virgin America; worst: American Eagle.
BUMPING: The rate of bumping passengers from flights fell 8 percent. Best: JetBlue Airways; worst: SkyWest.
COMPLAINTS: Consumer complaints to the government in 2013 dropped 15 percent from 2012 after rising 20 percent the year before. Best: Southwest Airlines; worst: Frontier.
One of the report's authors, Wichita State business professor Dean Headley, credited the drop in complaints partly to United Airlines. The company suffered several computer-network outages and grounded hundreds of flights in 2012 when it combined the United and Continental computer networks after a merger, but "got their act together" in 2013, he said.
Headley said the drop in complaints might also reflect "a certain amount of resignation" that "it's never wonderful for airline passengers."
No matter how much people gripe about airlines when they're among friends, very few of the millions of fliers ever bother to file a complaint with the government. The Department of Transportation, or DOT, received 9,684 complaints last year after getting 11,447 in 2012.
Chris Lopinto, CEO of ExpertFlyer.com and not involved in the academic report, said he believes that most consumers complain directly to the airlines instead.
"The DOT can't comp you miles or comp you a voucher -- only the airlines can do that," Lopinto said. "A passenger might not think to file with DOT."