Alaska Airlines resumed operations on Thursday after a tech outage that suspended all of its flights, three months after a similar incident.

"Alaska Airlines is experiencing an IT outage affecting operations. A temporary ground stop is in place," the Seattle-based company said on X.

It later said that it was "actively restoring our operations."

An advisory from the US Federal Aviation Administration (FAA) issued at 0513 GMT on Friday showed that some flights had resumed, though all departures to Seattle-Tacoma International Airport remain grounded.

The outage, which began around 3:30 pm (2230 GMT), "is not a cybersecurity event, and it's not related to any other events," Alaska Airlines, the fifth-largest US carrier, said in a statement.

The issue began "with a failure at our primary data center," it added, saying that "the safety of our flights was never compromised."

The ground stop also affects its subsidiary Horizon Air, according to Alaska Airlines and the FAA, but not Hawaiian Airlines.

Three hours after the announcement was made, some passengers complained about a lack of information.

"Everyone everywhere at SeaTac. No boarding no firm updates," said one X user, Jeff Lawrence, posting a picture of a jam-packed airport waiting room.

The airline experienced a similar outage on July 20, which lasted about three hours.

Alaska Airlines attributed the July problem to the failure of "a critical piece of multi-redundant hardware at our data centers."

Alaska last year also experienced an IT outage that caused disruption and delayed flights.

In January 2024, a door plug section of a new Boeing 737 Max 9 blew out during an Alaska Airlines flight between Portland, Oregon and Ontario, California.

The 171 passengers and six crew members survived the rapid decompression, but the FAA temporarily grounded many Boeing 737-9 aircraft operated by US airlines.  

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