Airlines in the U.S. are making vast improvements on key items affecting passenger experience, a new study says. But even still, complaints made by air travelers against their airlines are on the rise.

FOX's Eben Brown reports:

Airlines could boast their performance this past year, yet complaints by passengers are up more than a third:

(Headley) "And the industry actually improved as a whole. On-time, baggage handling, and denied boardings all were better than they were a year ago."

Dean Headley from Witchita State University and the airline quality rating. Passengers complain, he says, about high fares, despite the drop in fuel cost:

(Headley) "There's $11 billion came into their revenue stream that wasn't there in 2014, and what have they added? A little food and beefed up first class, business class? What have they done for the person in the back of the plane?"

Eben Brown, FOX News.