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.

Alaska Airlines warned of more flight disruptions on Monday after an unexpected failure of a critical piece of hardware at its data centers late Sunday forced it to halt all flights for about three hours.

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.