U.S. carrier Alaska Airlines ALK.N resumed operations late on Sunday after briefly grounding all of its flights for about three hours due to an IT outage, marking the second time it has halted its fleet in just over a year.

The company requested a system-wide ground stop for Alaska and Horizon Air flights at around 8 p.m. Pacific on Sunday (0300 GMT on Monday) after it said that an outage impacted its systems, and lifted the ground stop by 11 p.m. Pacific, the carrier said.

“As we reposition our aircraft and crews, there will most likely be residual impacts to our flights. It will take some time to get our overall operations back to normal,” the Seattle-based company said.

Alaska did not immediately specify the nature of the IT outage.

In April 2024, Alaska grounded its entire fleet due to an issue with the system that calculates the weight and balance of its planes.

Alaska Air Group maintains an operational fleet of 238 Boeing BA.N 737 aircraft, and 87 Embraer EMBR3.SA 175 aircraft, according to its website.

In June, Alaska Air Group-owned Hawaiian Airlines said some of its IT systems were disrupted by a hack. Alaska Air Group said it was still determining the financial impact of that event.

The news of Alaska’s IT issues comes at a time when tech companies Google and Palo Alto Networks have warned of the “Scattered Spider” hacking group’s interest in the aviation sector.

Canada’s WestJet Airlines was struck by an unspecified cyber incident in June, while Australia’s Qantas QAN.AX experienced a data breach in July where a cyber hacker accessed the personal information of millions of customers. But those incidents did not affect flying operations.

Separately, Microsoft said on Sunday that there were “active attacks” on its server software used by government agencies and businesses.

Alaska did not immediately respond to a request seeking comment on whether the outage was related to the Microsoft announcement.