Technicians worked to resolve a computer problem that prompted Alaska Airlines and its Horizon Air affiliate to cancel 152 flights, affecting at least 12,000 customers, officials said.
The presidents of both airlines said in a joint video statement on YouTube that Saturday's problem was caused by the failure of a system used for flight planning.
"A transformer blew and that took down the central computer system for both Alaska and Horizon," Alaska President Brad Tilden said during the two-minute statement released late in the afternoon.
A total of 152 flight were canceled, representing about 18 percent of the airlines' combined schedule, company spokesman Paul McElroy said late Saturday night. He said at least 12,000 customers were affected.
Other flights were delayed, and customers had trouble getting flight-status updates on the airlines' website because of the outage, McElroy said.
Both Tilden and Horizon President Glen Johnson apologized for the disruption. Johnson said stranded passengers would be rebooked on later planes or put on other airlines. The company said will not be charged a flight-change fee.
McElroy said the airlines worked on the problem throughout the day. Crews partially restored the system, but held off on the work needed for a full restoration until later in the evening when the flight load was lower, McElroy said.
"At this point, we hope that our operations will be normal" Sunday morning, he told the Associated Press.
Alaska Airlines uses versions of the Boeing 737 with roughly 124 to 172 seats, according to airline seating chart websites. Horizon uses smaller turboprop planes.
Seattle-based Alaska Airlines flies to cities in the U.S., focusing on the West Coast, and to Canada and Mexico. Alaska and Horizon are owned by Alaska Air Group Inc.
AP Airlines Writer David Koenig in Dallas contributed to this report.