NEW YORK (Reuters) - Despite a steady stream of headlines highlighting U.S. airlines’ customer-service failures, carriers have actually improved in several key areas over the last year, including bumping fewer passengers and losing less baggage, according to a study released on Monday.

FILE PHOTO: An Alaska Airlines plane is shown on final approach to land in San Diego, California April 4, 2016. REUTERS/Mike Blake/File Photo

The annual Airline Quality Rating (AQR), compiled by researchers at Wichita State and Embry-Riddle Aeronautical universities, found that U.S. carriers in 2017 recorded improvements in the number of passengers denied boarding, mishandled baggage and customer complaints, even as high-profile instances of customer-service failures continue to plague the industry.

The study’s findings showed that airlines improved their performance in everything but on-time arrivals, the most heavily weighted of the four components. In that category, there was a decline of 1.2 percent versus the previous year.

Airlines have sought to improve their public perception in the months following an April 2017 incident in which a 69-year-old United Airlines UAL.N passenger was dragged from his seat to make way for crew members.

“A year ago, everyone watched a video of a passenger being dragged off of a plane, and even in recent months, airlines have had to deal with negative publicity via traditional media and social media for everything from mishandled bags and extended delays to fights onboard and cancellations,” study researcher Brent Bowen said in a statement.

“But the results of the study show that they are making the effort – even if it may seem incremental to the traveling public.”

Based on data from the U.S. Department of Transportation, the AQR rated Alaska Airlines ALK.N the top carrier, followed closely by Delta Air Lines DAL.N on the basis of on-time performance, denied boarding, mishandled baggage and customer complaints.

Ranked lowest of the 12 reported airlines were ultra-low-cost and low-cost carriers Frontier Airlines in 11th place and Spirit Airlines SAVE.N at the bottom of the heap.

“Spirit Airlines is committed to improving reliability, Guest service, and the in-flight experience,” Spirit Airlines spokesman Derek Dombrowski said in a statement.

“It’s also important to note the Airline Quality Report does not factor other things that Guests love about Spirit, including the lowest fares in the industry and newest fleet of planes in the U.S.”

Frontier did not immediately respond to a request for comment.