(CNN) -- Severed telecommunications cables disrupted ticketing and airport check-in systems at Alaska Airlines on Monday, creating long delays and cancellations for thousands of passengers traveling at the end of a busy holiday weekend.
The Seattle-based airline said in a statement that it had to manually process passengers at key hubs after its Sprint network, which services ticketing, reservations and check-in, went down at 7:30 a.m. Pacific time. Service came back up around noon.
Seventy mainline and regional flights affecting some 6,000 passengers were canceled.
Delays, in some cases, reached four hours as the outage impacted operations at Seattle, Portland, Los Angeles and Anchorage.
Alaska said it expected a handful of additional cancellations and residual delays as it worked to restore normal operations.
The airline apologized to passengers, blaming the problem on a "network outage."
Sprint spokeswoman Crystal Davis said communication cables were cut nearly simultaneously about 2,000 miles apart, knocking out service to some customers in the Pacific Northwest.
The lines were severed near a railroad track between Chicago and Milwaukee and at a location between Tacoma, Washington, and Portland, Oregon.
Alaska said it would place delayed passengers on later flights or arrange travel on other carriers.
Passengers traveling on Monday and Tuesday were allowed to change their tickets in advance without paying a change fee. However, they were responsible for making up any difference in fares.
Low-cost Alaska is the 10th largest U.S. airline, according to Transportation Department data.