By late Saturday morning, the two airlines canceled 60 flights. Company spokesman Paul McElroy said the airlines have been able to operate about 20 flights during the day. The outage lasted intermittently for about seven hours before technicians fixed the system at 10 a.m. PT.
On top of the cancellations, many morning flights were delayed by two hours or more and the airlines said other delays were expected until the system is restored.
McElroy said displaced passengers will be rebooked without a fee. Customers were advised to call the airline to check on their flight before going to the airport.
The company was going through a routine upgrade of its computer system when something went wrong, said McElroy.
Seattle-based Alaska Airlines flies to cities in the U.S., focusing on the West Coast, and to Canada and Mexico.
The Associated Press contributed to this report.