The Seattle-Tacoma International Airport has confirmed that a cyberattack is likely behind the ongoing IT systems outage that disrupted reservation check-in systems and delayed flights over the weekend.

SEA-TAC is Seattle’s primary international airport and the busiest in the Pacific Northwest region. In 2023, it served almost 51 million passengers. The airport is a major hub for Alaska Airlines and Delta Air Line, servings 91 domestic and 28 international destinations.

On Saturday,  August 24, the Port of Seattle warned that it and the SEA Airport were suffering an ongoing outage caused by a “possible cyberattack,” forcing them to isolate certain critical systems to contain the damage.

“The Port of Seattle, including SEA Airport, is experiencing an internet and web systems outage, which is impacting some systems at the airport. Passengers are encouraged to check with their airlines for the latest information for their flights,” reads an X thread posted by the Port of Seattle.

“Earlier this morning the Port of Seattle experienced certain system outages indicating a possible cyberattack. The Port isolated critical systems and is in the process of working to restore full service and do not have an estimated time for return.  (Cont.)”

“We are working closely with appropriate authorities and partners to help travelers who may be impacted. If you are traveling today, please check with our airline partners for travel information and allow extra time to get to SEA and to your gate.”

The outages continued on Sunday, with the airport suggesting that people access travel information, such as gate numbers corresponding to their flights, on airline websites.

The airport’s website remains offline at the time of writing, while the official X handle warns passengers they should perform certain actions, such as check-in for their upcoming flights via their airline apps, as on-premise terminals remain out of order.

“System outages continue at the Port of Seattle, including at SEA airport,” reads the latest update from the airport operator.

“Port teams continue to make progress on returning systems to normal operations, but there is not an estimated time for return.”

Those traveling on Monday are recommended to:

• Check-in online and get your boarding pass before leaving.
• Stick to carry-on luggage if possible.
• Allow extra time to reach SEA and your gate.
• Confirm gate details with your airline, as flight screens are still down.

The system outages have not impacted flights. However, several people have been reporting multi-hour delays in some cases.

Alaska Airlines also took to X to inform its customers that its baggage sorting system is “extremely limited” at SEA, suggesting that people only bring the minimum essentials with them and avoid checking bags if possible.

Those in need of checking a bag are advised to add a tag with their full name and contact info on it. On its website, Alaska Airlines informs that this information will be used to track bags that have not appeared on the carousel upon arrival due to the current situation.

An FBI spokesperson confirmed to The Seattle Times that they “are aware of the incident and working with partners to determine what happened,” without disclosing any additional information.

No ransomware groups or other threat actors have taken responsibility for the attack at this time.