[UPDATED 4:30: All systems restored]

All American Airlines flights in the U.S. were grounded today by problems with its computer systems, the Federal Aviation Administration said.

American, the third-biggest U.S. carrier, initially told customers flight delays were being caused by its Sabre Holdings Corp. reservation and booking tool being offline. There are no problems with the Sabre system, which provides such services for most airlines, said Nancy St. Pierre, a spokeswoman.

The carrier requested a nationwide “ground stop” on all its flights because of computer problems, Lynn Lunsford, an FAA spokesman, said in an e-mail. He had no further details.

Mike Trevino, an American spokesman, said in an e-mail that the issue didn’t involve Sabre, without providing more detail.

Editors: Kevin Miller, Kevin Orland. To contact the reporter on this story: Mary Schlangenstein in Dallas at maryc.s@bloomberg.net. To contact the editor responsible for this story: James Langford at jlangford2@bloomberg.net. 

Photo Credit: American Airlines aircraft stand on the tarmac at Los Angeles International Airport. Lucas Jackson / Reuters