(From my story on msnbc.com’s Overhead Bin. )

Performance-wise, 2011 was a very good year for U.S. airlines. As an industry, overall performance was the best in the 21 years of the Airline Quality Rating 2012 (AQR) (PDF), a yearly report that crunches data such as lost bags, delayed flights, bumped passengers and customer complaints.

“This is not opinion. In almost two decades we have not had this level of optimum performance,” Dr. Brent Bowen, the head of the Department of Aviation Technology at Purdue University, told msnbc.com. Bowen conducts the AQR with Dr. Dean Headley, an associate professor at the W. Frank Barton School of Business, Wichita State University. The report was released April 2.

Despite the strong marks, however, air travelers don’t seem to notice. In the Airline Passenger Survey 2012 (PDF), also conducted by Purdue and Wichita State researchers and released Friday, more than half of frequent fliers polled reported being disappointed with the air travel experience.

“By the numbers, 2011 may have been the best year for the airlines,” said Dr. Erin Bowen, one of the survey’s authors and an assistant professor at Purdue University’s Department of Technology Leadership & Innovation. “But airlines are doing a poor job of conveying these improvements to passengers. The objective improvements don’t match up with the experience passengers are getting when they fly,” she said.

Among some other findings from the survey:

Fifty-four percent of frequent fliers don’t believe airlines are being completely honest by attributing fare and fee increases to rising fuel costs;

Given a choice of how to offset rising air costs, air passengers put a la carte fees, such as Allegiant Air’s recently imposed fee for carry-on bags, at the bottom of their wish list. “They’d rather pay a higher fee, take alternative transportation or fly less,” Erin Bowen said;

Passengers primarily rely on price and schedule when choosing an airline. When that is constant, however, travelers consider customer service (36 percent) and on-time arrival (32 percent) as factors.

In a ranking of the most passenger-friendly airlines, Southwest was an overwhelming favorite. More than one-third of frequent fliers surveyed put the low-cost carrier ahead of the 14 other airlines on the list. JetBlue was ranked No. 2 (12 percent), followed by Continental and Alaska (6 percent each).

Southwest also ranked No. 1 as the most preferred airline with 17 percent of the vote. Delta and United were close behind at 12 percent, followed by American (11 percent) and JetBlue (10 percent).

The gap between Southwest and its competitors has been shrinking. In 2009, the first year of the Airline Passenger Survey, the discrepancy between Southwest and Delta was 9 percent; the gap fell to just under 6 percent at the end of 2010, and now sits at 5 percent.

“Southwest has the lead, but other airlines are starting to do a better job of meeting consumer expectations and putting out a friendlier message,” Erin Bowen said.

Thanks for visiting Stuck at the Airport. Subscribe to get daily travel tidbits. And follow me on Twitter at @hbaskas and Instagram.