Alaska Airlines said Monday it had resumed operations after hours earlier requesting its fleet be grounded because of an "IT outage."
The airline apologized for the disruption, and urged travelers to check their flight status before heading to the airport — adding it "will take some time to get our overall operations back to normal."
The airline earlier told AFP it "experienced an IT outage that's impacting our operations" and that it had "requested a temporary, system-wide ground stop for Alaska and Horizon Air flights until the issue is resolved."
Before the grounding was lifted, the Federal Aviation Administration status page showed all destinations affected by the halt of Alaska's mainline aircraft.
"We apologize for the inconvenience," Alaska Airlines said in a statement.
"As we reposition our aircraft and crews, there will most likely be residual impacts to our flights."
In a separate statement posted on X, the airline said it has "resolved its earlier IT outage," without giving details.
The grounding drew a backlash from frustrated passengers.
"This is brutal. We've been sitting at the airport for two hours," wrote an X user named Caleb Heimlich in one of such replies.
"It's 10:20 pm, people are tired, hungry, etc. This is not okay," said another.
Alaska last year also experienced an IT outage that caused significant disruption to its operations, including delayed flights.
At the time, multiple users complained they were facing difficulties accessing its app and website.
Active attacks?
The airline's latest outage comes a day after Microsoft warned of "active attacks" targeting server software used by businesses to share internal documents and urged security updates.
Alaska Airlines did not immediately respond to AFP's request to clarify whether the outage was linked to the Microsoft issue.
The incident also comes more than a year after a door plug section of a newly delivered Boeing 737 Max 9 blew out during an Alaska Airlines flight between Portland, Oregon, and Ontario, California in January last year.
The 171 passengers and six crew members survived the rapid decompression, but the FAA later grounded many Boeing 737-9 aircraft operated by U.S. airlines.
Last month, U.S. investigators said Boeing's failure to provide adequate training to manufacturing staff was a driving factor in the near-catastrophic Alaska Airlines mid-flight blowout.
Alaska Air Group has a fleet of 325 aircraft, comprising 238 Boeing 737 planes and 87 Embraer 175 aircraft, according to its website.