After a seven-hour disruption that grounded planes across its entire network, Alaska Airlines said it restored its operations late Thursday.

But flight cancellations were already piling up for Friday.

Overnight, the Seattle-based carrier also warned that additional flight disruptions were likely still to come as it recovered from “a significant IT outage” that affected its entire network. The carrier issued a flexible travel waiver to flyers willing to change their travel plans.

The cause of the ground stop

Alaska Airlines initially requested a nationwide ground stop for its flights around 7:21 p.m. EDT (4:21 p.m. PDT) on Thursday, citing a tech outage that had affected its operations.

The disruption affected both Alaska’s mainline operation and its flights operated by regional subsidiary Horizon Air — but not Hawaiian Airlines, run by the same parent company as Alaska.

The ground stop led to massive flight delays and cancellations at the fifth-largest U.S. airline and saw passengers stranded at airports across the country, especially Alaska Airlines’ major West Coast hubs, from Seattle and Portland, Oregon, to San Francisco, Los Angeles and San Diego.

All told, Alaska Airlines’ outage led to some 229 flight cancellations, the airline said. That was on top of hundreds of additional delays. Alaska Airlines’ Seattle-Tacoma International Airport (SEA) home base was most heavily affected, with more than 10% of all departures canceled on Thursday, per FlightAware.

More travel woes expected Friday

Alaska Airlines was able to resume service around 2:30 a.m. EDT (11:30 p.m. PDT), the carrier reported, but cautioned that additional disruptions were likely as it repositioned aircraft after halting its departures for seven-plus hours.

By 7:30 a.m. EDT Friday, the airline had preemptively canceled 115 flights for Friday (or at least 14% of its network), according to data from FlightAware.

That number could grow on Friday as the airline gets its flight operations back on track.

“We appreciate the patience of our guests whose travel plans have been disrupted,” Alaska Airlines said in a statement. “We’re working to get them to their destinations as quickly as we can. Before heading to the airport, we encourage flyers to check their flight status.”

What to do if your flight is canceled or delayed

Late Thursday, Alaska Airlines issued a travel waiver to allow passengers additional flexibility to change or cancel their flights. The advisory covered flights with an original travel date of Thursday or Friday and allowed rebooking to any day between Thursday and Monday.

Passengers who encounter flight cancellations and major delays are entitled to a refund under U.S. Department of Transportation policies — that is, if they ultimately choose not to fly with the airline instead of accepting rebooking.

Read more: Flight canceled or delayed? Here’s what to do next

However, Alaska has also made a range of guarantees for passenger accommodations when there’s a major flight disruption within the airline’s control. Generally, an information technology outage falls under that category. Those details can be found on the DOT’s FlightRights.gov dashboard.

In the wake of Thursday night’s outage, Alaska Air Group also postponed its third-quarter earnings call that had been planned for Friday.

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