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 airline confirmed that the failure of a third-party piece of hardware grounded flights, underscoring the fact that even systems that are multiply-redundant can go down.

The US' Alaska Airlines saw flights grounded for around three hours on July 20 after an issue at its data center. As first reported by Reuters, flights were able to resume from 11pm Pacific time following an IT outage. At the time of reporting, it was not known that the issue was data center-related.