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 temporarily grounded on Sunday.Thousands of passengers have been affected by knock-on delays and cancellations continuing into Monday as the airline scrambles to resume service.

A hardware failure at an Alaska Airlines data center caused a system-wide “ground stop of flights” on Sunday night, the airline said. The airline has canceled more than 150 flights at various airports, including 64 Monday morning, with additional flight disruptions expected.