When road warrior Steve Bessellieu tried to get through to US Airways' customer-service desk for top-status frequent fliers by phone last month, the automated system didn't recognize his personal identification number and transferred his call to the lower-tiered Gold desk after three tries. Frustrated, he sent an email to the airline but has yet to hear back, he said.

"If this is how they're treating me, how are they treating the people who don't have status?" Mr. Bessellieu said.

US Airways Group Inc. faces substantial challenges in integrating operations following last year's merger between the old US Airways and America West Holdings Corp. Among them, it has to keep inevitable technology glitches from alienating its customers. Last month, the merged airline launched a combined Web site and merged frequent-flier programs by migrating more than 10 million records from one airline's technology platform to another. The outcome has been far less than perfect.

"This is one of the things that makes airline mergers really hard," said Travis Christ, US Airways' vice president of sales and marketing. "One of the frustrations that our customers feel sometimes -- and we do, too -- is that this just takes time. You can't measure it in hours and days."

While the merged airline's Web site now appears uniform to users, there are still two separate reservations systems in the backdrop. That means those two systems, both antiquated, must communicate with each other behind the scenes to process bookings properly. Even bigger potential troubles could come from merging the two systems, which is planned for the first quarter of next year.

US Airways officials concede there have been problems with the Web site. It has had trouble booking tickets and doing online check-in, a feature the airline touts as a customer convenience. The site has been slow -- functions like moving from page to page have taken up to twice as long during high-volume periods.

The airline said complaints to its call centers rose the day after the May 21 launch of the new Web site. But airline officials say problems were more the exception than the rule, and have since been largely corrected. On the fifth day after launch, for example, officials addressed slowness issues by reconfiguring servers to run off of some very fast disk drives. That change sped things up online by about 50 percent, the company said.

"Every hour, we're finding things and getting them knocked out," US Airways' Mr. Christ said. He said the company purposely opted to do a "soft launch" of the site, which means it didn't announce the unveiling to customers. If it had, the site might have crashed amid traffic overload. Chief Information Officer Joe Beery said a team of 60 to 70 people are onsite near the company's Tempe, Ariz., headquarters managing the process.

Mr. Bessellieu, the frequent flier, complained last week that he still couldn't look up his current frequent-flier account online, something the company says it knew in advance might occur until updates are completed June 9. He had further problems Memorial Day weekend viewing the seat map for a flight he was trying to book, and says airline staffers haven't been much help. "The agents that I've spoken to seem as lost as I do," he said.

Meantime, customer calls are pouring into the airline's 24-hour Internet help desk. On a recent afternoon, a call to the desk required holding for 30 minutes before getting an actual person to pick up the phone. An airline spokesman said many of the calls are from people inquiring about why their frequent-flier accounts aren't updating. Others are customers calling in to get help logging in to the new Web site for the first time, since frequent fliers have to create a new user profile for their accounts. The company said it increased staffing by 20 percent ahead of launch to handle higher call volume.

For its part, US Airways says it has received compliments on the new site as well. And the site does have some improvements. Users of the old USAirways.com will now have an improved booking engine with a feature that helps them determine which travel days have lower fares, for example. And users of the old America West site will be able to book United Airlines flights online through a code-share agreement.