The problem was affecting the airline's ability to check in passengers and make reservations, and it affected flight operations, the carrier said.
Alaska Airlines said its Internet provider, Sprint, went down at 7:30 a.m. PST after a fiber network cable was cut in Wisconsin. Sprint links the airline to the SABRE system used for reservations, check-ins and ticket purchases.
"The outage is preventing customers from checking in and has caused significant systemwide delays in all cities Alaska Airlines serves," the airline said.
"Alaska Airlines has implemented a manual process to check-in customers, however, this process will be slow and flights will depart late. If this problem persists, we will most likely cancel [some flights]."
No flights had been canceled as of 10 a.m. PST.