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 flights were grounded due to a tech failure, causing nationwide disruptions and residual delays.

Alaska Airlines and its regional subsidiary Horizon Air requested a ground stop to all flights Sunday night due to a computer system outage. The request to federal authorities kept Alaska and Horizon flights out of the air until the FAA said the stop was lifted after 2 a.m. ET. Monday.