Despite widespread perceptions that airline service is deteriorating, 2011 was the "best year ever" for airline performance, according to independent experts who have been studying data for the past 21 years.

Air travelers were less likely to be bumped, less likely to lose their luggage and more likely to arrive at their destinations on time, according to the Airline Quality Rating report released Monday in Washington. Consequently, passengers filed fewer complaints with the government, the report says.

The change is a remarkable turnaround from just four years ago, when airline performance was at a historic low, said Dean Headley of Wichita State University, who co-authored the report with Purdue University professor Brent Bowen.

"Everything is heading in the right direction," Headley said.

Headley said the improvement is similar to a trend witnessed after the Sep. 11, 2001, terrorist attacks, when a drop in volume eased congestion and led to fewer delayed flights. Because of the recession, airlines have lower volumes but have increased the number of full seats.

"So the planes are full; not as many planes, system works better, performance is better," Headley said.

The most dramatic improvement in 2011 was a 30% cut in the number of people involuntarily bumped from flights, Headley said. The number was 0.78 of every 10,000 passengers, down from 1.08.

Airlines also continued to chip away at flight delays and misplaced luggage. And customer complaints to the Department of Transportation were flat, he said.

"What's interesting is, while the ... numbers are showing the airline performance is getting better ... the customer doesn't think so," Headley said. "They may not always pay attention to these numbers."

Three low-cost airlines -- AirTran, Hawaiian and JetBlue -- again got the top ratings in the study, as they did last year. Frontier Airlines climbed from ninth place last year to take fourth place, making it the "most improved airline," Headley said.

American Eagle got the lowest ranking of the 15 airlines included in the study.

American Eagle didn't agree with the assessment. A company spokesman dismissed the report as unscientific, saying it was based on "mostly old data" and reflected the opinions of its authors.

"We don't have any specific comment as to how much, or if, customers should put stock in the government and private reports that regularly come out. We will say that in our own surveys of our own customers, their reasons for choosing an airline put many, many other reasons above government and private surveys," spokesman Ed Martelle said.

Martelle said it is not coincidental that the airlines at the bottom of the list are regional ones. "Regional carriers fly very different missions vs. mainline airlines," he said. They fly shorter distances and are more prone to weather and air traffic control disruptions.

Headley said he is not sure why low-cost airlines get the highest customer satisfaction ratings, but he believes it may be connected to customers' expectations.

Low-cost carriers keep their promise simple, Headley said. "We're going to get you there, and we're going to try not to hassle you and we're going to give you a good price," he said.

"Generally that's what the consumer is looking for. So their perceptions of what they're getting for what they paid probably match up better, so they complain less."

The Airline Quality Rating is based on statistics that the airlines provide to the government. "While issues arise from time to time, the overall performance is reliable, safe, efficient and affordable," the report's authors said.

An airline industry group did not comment on individual airlines, but touted the improved performance.

"Our members are committed to and are delivering levels of safety and customer service that no other industry, given its complexity, matches," said Steve Lott, a spokesman for Airlines for America.