Frequent business traveler John Steinberg has little tolerance for travel websites that are slow or fail to smoothly process a transaction.

"I am a low-tech person," says Steinberg, a consultant in Randallstown, Md. "If the site frustrates me, I either call the hotel or airline or use another provider."

Steinberg is part of a growing market of travelers who plan or book their trips on the Internet.

Online travel bookings worldwide last year were expected to total a record 375 billion - up from 337 billion in 2011, according to market research company PhoCusWright.

Airlines, hotels and online travel agents increasingly seek to capture a bigger piece of the market, but websites vary in customer friendliness.

Compuware, which monitors website performance, looked at the most trafficked airline, hotel and travel agent websites in 2012 for its fourth annual Best of the Web awards, and, at USA TODAY's request, chose the top five performers.

AirTran Airways was named the best-performing airline website, Best Western the top-performing hotel site and Resort Vacations To Go the best-performing travel agent site.

The companies with top-performing websites "are dedicated to making sure their customers get the best experiences online," says Stephen Pierzchala, Compuware's technology strategist. "A poorly performing website can negatively impact an organization's brand and revenue."

Compuware's website performance scores indicate customer friendliness. They don't evaluate a site's content or indicate which one is best for consumers, Pierzchala says.

To track website performance, Compuware uses specially installed monitoring software in tens of thousands of desktop and laptop computers throughout the U.S.A.

Performance is judged by each website's average response time, availability and consistency.

Response time is the time elapsed downloading each Web page or transaction. Availability is the ability to access a website, process a transaction without error and download each transaction step within 60 seconds. Consistency measures the consistency of a website's response time each time a user visits.

AirTran's website had an average response time of 5.29 seconds, the fastest time of any U.S. airline's website. (AirTran has been acquired by Southwest.)

The websites of two other U.S. carriers, Allegiant Air and Alaska Airlines, and two foreign airlines, Hong Kong-based Cathay Pacific and Chile-based Lan, also finished in Compuware's top five in performance.

Allegiant's average response time was 5.79 seconds, and Alaska's average response time was 6.38 seconds.

Slow website response times can cause airlines or other companies to lose online business. Studies have shown response times above two or three seconds are slow enough to cause viewers to leave a website, Pierzchala says.

Air France's site, which had an average response time of 12.93 seconds, finished last in performance of the 20 most-trafficked websites monitored by Compuware.

United Airlines and Delta Air Lines, which had average response times of 11.20 and 10.26 seconds, respectively, also finished near the bottom in performance.

Staying on Site

Of the 20 most-trafficked hotel websites, Best Western was the best performer, followed by Marriott and Omni. Best Western's site had an average response time of 4.36 seconds, about a half-second faster than Marriott's site.

Planet Hollywood, a resort and casino in Las Vegas, had the slowest average response time, 19.91 seconds.

Of the 20 most-trafficked online travel agent websites, the best-performing, Resort Vacations To Go, had an average response time of 3.03 seconds.

Other sites in the top five for performance were TripRes, Trip Mama, Hotel Guides and Virgin Vacations.

More popular sites, Orbitz and Travelocity, finished near the bottom of the list. Orbitz's average response time was 8.22 seconds, and Travelocity response time was 7.65 seconds.

Compuware also tracked the travel industry's best-performing mobile websites (not apps) last year while using carriers Verizon, Sprint and AT&T. Among nine mobile sites of travel agents that were monitored, Kayak was the best performer, followed by Travelocity and Hotels.com.

Of 15 mobile websites of hotels that were monitored, Fairmont finished No. 1, followed by Best Western and Omni.

Lan finished first among 13 airlines' mobile websites, followed by AirTran and a tie for No. 3 by Delta and American.

The average response times of some airlines' mobile sites were relatively long.

Korean Air's mobile website had an average response time of 36.73 seconds. Lufthansa, the German airline, had an average response time of 21.73 seconds.

Steinberg, the Maryland-based business traveler, says response time is "extremely" important when he goes to travel websites. "Slow loads are no-goes," he says. "I frustrate easily with technology and will switch to an easy site to use rather than stick with a balky one."

Frequent business traveler Sue Reiss of Marathon, Fla., says poor-performing and slow-response websites frustrate her, too. "Any delays in booking my trips are not just inconvenience but enough to make me go to a vendor who has a user-friendly website," she says.