Alaska Airlines flight cancellations and delays grew Monday after the carrier requested a ground stop during an outage Sunday night.

Over 400 flights were delayed or canceled at Sea-Tac Airport due to an Alaska Airlines IT outage. The outage was caused by an unexpected hardware failure at Alaska Airlines' data centers. Alaska Airlines flights have resumed, and passengers are asked to check their flight status before heading to the airport.

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.