Besides performing many functions, airline computer systems might be assembled or serviced by different vendors. For American, the complexity will be magnified when it combines reservations, scheduling, frequent-flier and other programs with those at US Airways.
"They have to merge all the data from US Airways over to the American system. There could be huge translation problems" if the two airlines' systems use different coding, said Bill Curtis, senior vice president of CAST, a business software-analysis firm.
"They'll probably have some hiccups," Curtis said. "They may be big ones, or they may be so small that the public never notices."
AMR did not immediately respond to a request to make its chief information officer, Maya Leibman, available for an interview. She has been American's top technology officer for a little more than a year, replacing an executive who resigned shortly after AMR filed for bankruptcy protection in November 2011.
The term "information technology" appeared only three times in AMR's latest annual report filed with the Securities and Exchange Commission, and the company has provided few details on how much it spends to improve and maintain its computer systems, or who does all the work.
AMR said in the annual report that it has "engaged an increasing number of third-party service providers" for many jobs, including information technology hardware and services. The report also said the company will spend at least $80 million this year and $70 million in later years on a single IT-support contract.
US Airways CEO Doug Parker will run the new company after the merger. He has said he would prefer to convert his company's computer systems to American's since American is larger. He has pointed to the technology breakdowns that occurred after the United-Continental and US Airways-America West mergers, when the larger airline adopted the smaller one's systems.
For a second straight day Wednesday, US Airways declined to comment on whether Parker would reconsider his plans considering American's nationwide outage.
Associated Press Airlines Writer Joshua Freed in Minneapolis contributed to this report.
David Koenig can be reached at http://www.twitter.com/airlinewriter .
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