A computer outage forced Alaska Airlines and its subsidiary Horizon Air to ground all flights Sunday night, halting operations across the board. On Monday, the airline said that operations were coming back online.

The airline requested a system-wide ground stop from federal aviation authorities at about 11 p.m. ET on Sunday night. That stop remained in effect until around 2 a.m. ET Monday, when the Federal Aviation Administration confirmed it had been lifted. But disruptions didn’t end there. Alaska warned passengers to brace for likely delays throughout the day.

“We are currently experiencing an IT outage that’s impacting our operations,” Alaska Airlines posted on X shortly after midnight on Monday. “We requested a temporary, system-wide ground stop until the issue is resolved.” 

The FAA’s website listed the stop as applying to all Alaska Airlines aircraft. The airline did not share details about the cause of the issue and did not immediately respond to a request for comment from Gizmodo.

However, the company posted on X that passengers should check flight statuses before heading to the airport, as the outage could continue to disrupt travel. The company warned that as it repositioned its aircraft and crew, there would likely be “residual impacts” to its flights. 

“Alaska Airlines has resolved its earlier IT outage and has resumed operations. We sincerely apologize for the inconvenience, and encourage guests to check your flight status before heading to the airport,” the company posted on X. 

Travelers took to social media to vent about long delays on the tarmac and in terminals, particularly at Seattle-Tacoma International Airport. One said they endured five gate changes. CNN reported that some passengers were stuck on planes for hours.

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.

The incident comes almost exactly one year after a software update from the cybersecurity firm CrowdStrike caused a global IT outage. The crash has become known as the largest IT outage in history. The July 2024 outage brought down an estimated 8.5 million Microsoft Windows systems running CrowdStrike’s Falcon Sensor software, disrupting everything from hospitals and airports to broadcast networks.

There’s no word yet from Alaska on whether the outage ties into a broader software problem, but the timing, almost exactly a year after the CrowdStrike crash, isn’t going unnoticed on social media, with users wondering if the events are related.