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.

Alaska Airlines has revealed that an "unexpected failure" of a critical piece of hardware caused an IT outage that led to its entire fleet being grounded.

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.