The computerized reservation system for American Airlines failed for nearly 12 hours Friday, hindering flight scheduling and other arrangements for travelers around the world.

John Hotard, a spokesman for the airline based in Fort Worth, Texas, said the Sabre II computer reservation network went down shortly after midnight and was reactivated just before noon Friday.The computer network, based in an underground bunker in Tulsa, drives the American Airlines computerized reservations worldwide and provides services to more than 14,000 other organizations, including car rental companies, hotels and a third of all U.S. travel agencies.

"A lot of people suffered frustrations," said Eric Munro, chapter president in San Diego of the American Society of Travel Agents. "In the day of computers, we just have nothing to do when this happens. It's a way of life for us. What can you do?"

Hotard said there was no immediate explanation for the computer failure, which forced airline reservations to be written by hand and confirmed later. "It was not a personnel problem. It had something to do with a problem in our Tulsa office," he said. "If we know the reason, we are speculating and we're not saying at this point."

Hotard said technicians will study the system over the weekend and should have more information next week.