Airline passengers filed 11,445 complaints with the Department of Transportation last year, an increase of more than one-fifth from 2011.
The rate of complaints per 100,000 passengers also rose, from 1.19 in 2011 to 1.43 last year.
A breakdown of that rate for the 14 largest U.S. carriers from a report on airline quality by researchers at Purdue University and Wichita State University. The report is being released Monday. 2011 rates were not available for ExpressJet and Virgin America.