The Seattle-based carrier confirmed the incident in a statement, saying the issue began around 8pm Pacific Time (0300 GMT Monday) and led to a temporary system-wide ground stop for both Alaska and Horizon Air flights. The airline did not disclose the exact nature of the outage.

“We requested a temporary, system-wide ground stop for Alaska and Horizon Air flights,” the company said, adding that the disruption would cause residual impacts throughout the night.

The Federal Aviation Administration (FAA) has not yet commented on the matter.

However, the FAA’s status page confirmed that all destinations were affected by the ground stop impacting Alaska’s mainline aircraft and Horizon Air operations.

Alaska Air Group, the parent company of Alaska Airlines, operates a fleet of 238 Boeing 737 aircraft and 87 Embraer 175 jets, according to its official website.

This latest disruption comes shortly after the company-owned Hawaiian Airlines suffered a cyberattack in June, affecting some of its IT systems. Alaska Air Group is still assessing the financial fallout from that incident.

The grounding also follows a serious safety incident from January last year, when a door plug on a newly delivered Boeing 737 Max 9 detached mid-flight during an Alaska Airlines journey from Portland to Ontario, California.

All 171 passengers and six crew members survived the rapid decompression, but the incident led to the FAA grounding many Boeing 737-9 aircraft across U.S. airlines.