Reliable, yet inflexible legacy systems were partly to blame for the glitch in US Airways Group's self-serve kiosk system> that led to long lines and delayed flights earlier this month, according to an e-mail sent to the airline's frequent fliers by a company executive.

The glitch was tied to the integration of reservation systems with America West Airlines. US Airways was using a system by Sabre Airline Solutions, while America West was using Electronic Data Systems's Shared Airline Reservations System (SHARES). The two airlines, which merged in 2005, are now operating on the SHARES system.

"When we transferred the 7 million reservations from one system to the other, approximately 1.5 million of them didn't 'sync up' correctly, and our agents had to hand-process each reservation," said H. Travis Christ, the airline's vice president, sales and marketing, in the e-mail. "Many systems that were otherwise ready to go became bogged down with these reservations. We've since whittled the number of 'out of sync' reservations to a very small number."

In a telephone interview, Christ explained that most airline computer systems were built on legacy mainframe systems from the 1960s and 1970s. These systems are deeply embedded with everything like reservations, flight operations, airport operations and accounting.

"They are very reliable, but very inflexible. As our business changes, it's as though we're fighting with one hand tied behind our back," he said in the e-mail to customers.

In the interview, Christ said these legacy systems were revolutionary at the time they were built, and they helped the airlines to move away from keeping reservations on 3x5 note cards. Then came air-travel software systems like Sabre, which coincided with the deregulation of the airline industry and the rapid growth of the business, Christ said.

But as more modern Web-based systems were introduced and the level of expectations of the technology changed from a business to a customer perspective, it became clear these legacy systems were nearing the end of their useful lives, he said.

US Airways CIO Joe Beery said there's nothing wrong with mainframes, but rather the concepts behind the architecture of the systems. Beery said the legacy systems were developed based on the premise that airlines used paper tickets. However, now that airlines use electronic tickets, those systems are outdated.

So the problem, Beery said, is that when it's time to make changes in the legacy systems or when there's a merger, IT has to continually rebuild those concepts.

"So it's the framework and how the architecture of the systems are built that really hold us back," he said. "There really isn't any [modern system] operating in the industry, at least for major carriers, that you would consider a modern architecture."

Both Christ and Beery acknowledged that ultimately US Airways will have to move to a more modern system, but they also know that system doesn't exist yet.

Airline analysts agreed that the airlines are facing an uphill battle in trying to adapt technology to the changing airline industry.

"There are two issues here. One issue is migration from one to another, which was problematic. The other issue is the functionality of legacy systems versus new generation systems," said airlines' analyst Bob Mann, president of R.W. Mann & Co.

"I've done this on numerous occasions as a consultant in numerous places around the world, and I've never had a screw up like that so I'm not sure why that happened," Mann said.

Mann added there is no new system that can handle all the functions needed by the airlines.

"They'd like to be on new generation systems so they can check revenue production moment by moment, but no new generation system can handle all the requirements that a legacy airline has," Mann said. "We're talking years, not months, for a new generation system to be developed. If one existed, everyone would be standing in line for it."

Henry Harteveldt, an analyst at Forrester Research, said reservation system conversions are never as easy as people think they'll be. But US Airways took every step it possibly could have from a technology standpoint to address the challenge.

"But I don't think they understood all the implications, and they really failed by not having enough staff at key legacy US Airways hubs to help agents," Harteveldt said. "And I do believe that US Airways may have underestimated some aspects of the complexity of the migration, and in addition it came at a peak time -- spring break travel season."

Harteveldt said US Airways made its decision based on cost and the belief that it would be less inconvenient to disrupt America West than to disrupt US Airways.

"It's wrong to blame legacy systems -- it's disingenuous -- it's like they did eeney, meeny miney, moe [looking for something to blame]," he said. "A business person reading this would have said, 'Why didn't you just wait six months or a year.'"

Harteveldt said when US Airways migrated its reservation system, it was akin to doing both a brain surgery and a heart transplant at the same time, while throwing in a little plastic surgery for good measure.

Harteveldt said legacy systems are not as flexible as airlines would like, but both the Sabre and the SHARES systems have been modernized to some degree to make better use of service-oriented architecture and Web services to reduce their reliance on closed-end languages and to make the systems more flexible.

"It's very popular within the industry to blame legacy IT systems, and to an extent [Christ's] certainly right, but there have been transitions that have been successful and those don't get a lot of publicity," said Douglas Quinby, an analyst at PhoCusWright Inc. in Sherman, Conn.

Beery said there will come a time when [all the airlines] will have to make a decision to move on to modern systems.

"Legacy systems are not going to go away tomorrow, but we can't continue to operate forever using technology that was developed in, and ties us to, the 1970s," Christ said.