A computer glitch in the flight operations systems of US Airways and American Airlines, both of which are hosted by Electronic Data Systems, caused flights to be grounded for about three hours on Sunday (1 August).
US Airways Group grounded its flights Sunday morning to process flights and restore the automated system. It said about 100 flights were delayed. A spokeswoman referred further questions to EDS.
"We can confirm there was an issue with the flight operations system serving US Airways and American Airlines," said Kevin Lightfoot, a spokesman for EDS. "Our investigation indicated that it was an unintentional human error" that caused the problem, he added.
He declined to say whether the error was caused by an employee at EDS or at one of the airlines.
Lightfoot said EDS's operation teams caught the problem early and took the system down in an orderly, proactive fashion to fix it and prevent a more extensive system outage.
He said that the flight system was back up and running within three hours and that public safety wasn't affected in any way.
An American Airlines spokeswoman agreed that the safety of air travelers was never in jeopardy. She said it was her understanding that the glitch was caused by a technical error.
"There was a technical error that made our flight operations system go down. That [system] does everything with our crew scheduling, it does things with our flight plans," said Jacquie Young, a spokeswoman for American Airlines.
Young said that the glitch caused two-hour delays systemwide and that nearly all of the airline's 2,200 daily flights were affected because of a "ripple effect".
Linda Rosencrance writes for Computerworld
Read more on Operating systems software
British Airways passengers suffer flight delays due to another IT glitch affecting London Heathrow
British Airways cancels flights due to technical issue
BA IT systems failure results in cancelled flights and delays at London airports
British Airways settles legal claim with CBRE over May 2017 Bank Holiday datacentre outage