Updates with details and background in paragraphs 6, 9-12

July 20 (Reuters) - U.S. carrier Alaska Airlines ALK.N grounded its flights after an IT outage on Sunday that affected its systems, the company said, without specifying the nature of the outage, marking the second time it has grounded its fleet in just over a year.

"At approximately 8 p.m. Pacific on Sunday (0300 GMT on Monday), Alaska Airlines experienced an IT outage that's impacting our operations. We requested a temporary, system-wide ground stop for Alaska and Horizon Air flights," Alaska said in an emailed statement to Reuters on Sunday evening.

The Seattle-based airline said there would be residual impacts to its operations throughout the evening, without providing more details.

The FAA did not immediately respond to Reuters' requests for comment outside regular business hours.

The FAA status page showed all destinations affected by the ground stop of Alaska's mainline aircraft, and the suspension of Horizon's operations.

In April 2024, Alaska grounded its entire fleet due to an issue with the system that calculates the weight and balance of its planes, just a few months after a door panel on an Alaska Airlines-operated Boeing 737 MAX 9 jet blew off midair .

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.

It remains unclear whether Alaska's outage is related to Microsoft stating 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.

(Reporting by Gursimran Kaur and Shivani Tanna in Bengaluru; Editing by Rashmi Aich, Jamie Freed and Kate Mayberry)

((GursimranKaur.Mehar@thomsonreuters.com;))