The outage was a result of an unexpected hardware failure in Alaska's data centers and is not related to cybersecurity issues, the airline said.

Alaska Airlines operates 238 Boeing aircraft, 87 Embraer planes, and 45 additional planes through Horizon Air. The Seattle-based company is the fifth-largest airline in the U.S., serving more than 44 million passengers annually.

Alaska Airlines has resumed operations following an undisclosed technical error affecting its entire system for approximately three hours.