Alaska Airlines flights were back late Sunday night after an IT outage forced the company to ground all flights for three hours. From 8 p.m. until 11 p.m. PST, Alaska Airlines planes were on hold. The airline did not reveal the nature of the outage.

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.

Alaska Airlines has resumed flights after the failure of a critical piece of hardware forced the airline to ground all its planes for approximately three hours