UPDATE 3:30 p.m.: American Airlines posted a note on its Facebook page saying the system had been restored but that delays and cancellations will occur for the rest of the day.
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UPDATE 3:15 p.m.: Passengers appear to be getting boarding passes and are passing through security at American Airlines gates.
The problems started in late morning, and by about 1:40 p.m. American said on its Twitter account that it had ordered a system-wide ground delay until 4 p.m. CDT as it worked to fix the problems.
"We're working to resolve the issue as quickly as we can. We apologize to our customers for any inconvenience," American spokeswoman Andrea Huguely said in a statement.
The Federal Aviation Administration said it issued the ground-stop of American Airlines and American Eagle flights at the request of the carrier.
In a statement at 2:30 p.m. CDT, American said its network system is experiencing intermittent outages. The carrier offered to change customers' reservations at no charge if their travel plans are flexible. If not, American said it will provide full refunds.
But because of the computer problems, American said it can't make the changes to current travel plans until the computer issue is fixed.
After the problem began, flights at DFW were delayed with a few aircraft sitting on the runways, but not taking off.
“We’re seeing some planes on the tarmac that haven’t departed at this point. We’re mobilizing resources to help where we can. If that means helping deboard aircraft we’re ready to do that," said DFW Airport spokesman David Magana.
According to posts on Facebook and Twitter, some passengers have been stuck in planes waiting to take off for almost two hours with the computer outage affecting American's check-in and boarding system nationwide.
Sabre reservation spokeswoman Nancy St. Pierre said there are "no issues" from the Southlake-based company's system but that there is a connectivity problem which Sabre does not manage for American.
Website flight tracker, FlightStats.com, shows 321 American Airlines flights and 206 American Eagle flights have been cancelled as of 2:30 p.m. CDT. There are also 384 American Airlines flights and 323 American Eagle flights that have been delayed.
Most of the cancellations and delays are at DFW and Chicago O'Hare airports, two of American's major hubs.
PHOTO: American Airlines computer system went down late Tuesday morning, leaving the airline unable to check in passengers or allow flights to depart. (Star-Telegram/Max Faulkner)