Hundreds of Alaska Airlines flights and thousands of passengers’ travel plans were disrupted over the weekend and well into Monday following a “significant IT outage” that resulted in the grounding of planes for about three hours.

The failure, in the airline’s computer network, forced it to ground flights Sunday night for about three hours. The outage, tied to third-party equipment, yielded about 200 cancelled flights. A replacement is underway.

The outage was a result of an unexpected hardware failure in Alaska's data centers and is not related to cybersecurity issues, the airline said.