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.

In a statement earlier, Alaska said the outage involved its information technology network and was “impacting our operations.”

“We’re having problems with our IT systems. We apologize for any inconvenience and are actively working to fix the issues,” stated a message on the airline’s website.

Even as the problem is now resolved, it could have a lasting effect and cause delays to the airlines’ schedules through Monday.

“There will be residual impacts to our operation throughout the evening,” Alaska said in its earlier statement.

Alaska and Horizon Air ticket holders were asked to check the statuses of their flights before they arrived at their departure points.

Almost exactly one year ago, a sensor configuration update from the cybersecurity firm CrowdStrike triggered a crash in its widely used platform, impacting airlines, medical centers, businesses, and police departments worldwide and causing Microsoft computers to display “blue screens of death.”

The exact cause of Sunday’s Alaska outage was not immediately clear.