US carrier Alaska Airlines grounded all of its flights after experiencing an IT outage that impacted its systems, the company said, without specifying the nature of the outage.

"At approximately 8pm Pacific on Sunday [11am on Monday Hong Kong time], 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 on Sunday.

It resumed operations three hours later.

The Seattle-based airline said there would be residual impacts to its operations throughout the evening.

The Federal Aviation Administration's status page showed all destinations being impacted by the ground stop of Alaska's mainline aircraft, and Horizon's ground stop.

Alaska Air Group maintains an operational fleet of 238 Boeing 737 aircraft, and 87 Embraer 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 the hack. (Reuters)