Flying these days can seem like a major hassle. While overall airline performance is up, so is the number of customer complaints.

The 2013 national Airline Quality Ranking shows overall airline performance last year was at the second highest level compared with all of the annual results in the 23 years of the ranking. The ranking looked at airlines' performance in four areas: on-time performance, baggage handling, involuntary denied boardings and customer complaint rates. Overall, the industry improved in 2012 on the first two, but did worse on involuntary denied boardings and customer complaints.

The 2013 AQR, release in April, ranked the nation's 14 major airlines and is a joint research project funded as part of faculty research activities at Purdue and Wichita State University.

"During 2012 the industry improved the mishandled baggage rate by 8 percent, suggesting that most airlines are working hard to accommodate customers. Still, nearly a third of the customer complaints for 2012 were for flight problems, such as unplanned schedule changes, delays and cancellations," said Dean Headley, associate professor of marketing at the W. Frank Barton School of Business at Wichita State, when the results were released.

Added Headley: "When you look at the past 13 years, you find that the airline industry performs most efficiently when the system isn't stressed by high passenger volume and high number of airplanes in the air. Every time there are more planes in the sky and more people flying, airline performance suffers."

The challenge is whether airline performance quality improvements can be maintained as more people choose to fly, the researchers noted. Or, does the infrastructure and air traffic control technology limit what airlines can do?

What follows is AQR's ranking, from worst to best:

No. 14