BOSTON (AP) — The computer problem that caused delays and long check-in lines for multiple airlines at airports across the nation on Friday morning is being blamed on a hardware failure.

Sabre, the company that multiple airlines use for flight check-in services, said it experienced an outage that affected several customers.

Sabre in a statement said a hardware redundancy failure impacted its system, including product-service systems and check-in.

The issue has been resolved and efforts are underway to understand why the failure occurred.

The problem affected American Airlines, JetBlue and Alaska Airlines, including several American Airlilnes flights at Rhode Island’s T.F. Green Airport in Warwick, where a spokesman said most of the problems were resolved by 7:30 A.M.

Even after the system had been restored, there were reports of long lines at some airports hours later.