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' 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 However, now that airlines use electronic tickets, those systems are outdated.

For more enterprise computing news, visit Computerworld. Story copyright Computerworld, Inc.