Washington ? Three of the top four airlines in 2003 were low-cost carriers, with JetBlue Airways leading the pack with the best overall performance, according to an annual study released Monday.

The study’s authors say the report showed why low-fare airlines are gobbling up market share from traditional network carriers: They’re on time more, they bump fewer passengers, they mishandle less baggage and they generate fewer complaints.

The report “adds further evidence to the emerging performance gap between the legacy carriers and the no-frills network carriers,” said Brent Bowen, director of the University of Nebraska’s aviation institute and a co-author of the study.

JetBlue had the second-best on-time performance, arriving punctually 86 percent of the time in 2003, the first year that the airline carried enough passengers to be ranked. So few JetBlue passengers were bumped that they did not register in the statistics used by researchers.

JetBlue customers also filed fewer complaints — 0.31 per 100,000 — to the Transportation Department than all other airlines but Southwest.

Southwest, with 0.14 complaints per 100,000 customers, consistently generates the lowest complaint rate in the industry. It was rated as the No. 3 carrier in the report.

Alaska Airlines came in second, America West fourth and US Airways, ranked No. 1 last year when it was still in bankruptcy, was fifth.

Northwest Airlines, which came in sixth, was the most improved airline in 2003. It ranked ninth in 2002.

David Neeleman, founder and CEO of JetBlue Airways, helps the cleaning crew prepare an aircraft for the airline's inaugural trip to New Orleans at New York's John F. Kennedy International Airport in this July 26, 2001, photo. According to an annual study released Monday, JetBlue was No. 1 in performance among U.S. airlines in 2003.

The study’s authors said the low-cost airlines performed well in ways that were important to passengers.

Dean Headley, the other co-author and an associate professor of marketing at Wichita State University, said most of the low-cost carriers were above the industry average on four performance indicators last year. Most of the traditional airlines were below the industry average, he said.

“The low-fare carriers are definitely solid in their ability to attract passengers, and it shows in the market share gains that they’re making,” Headley said.

He said low-cost airlines comprised 4 percent of the market when he began the study in 1991; now they carry one-quarter of all passengers. Headley expects them to transport four in 10 by 2006.

The report rated the 14 U.S. airlines that carried at least 1 percent of the 587 million passengers who flew last year.

Four low-cost carriers — AirTran, ATA, Atlantic Southeast and JetBlue — met that threshold for the first time in 2003.