Alaska Airlines announced Sunday evening all of its flights, as well as those of its affiliate Horizon Air, are being grounded due to a software outage of an unspecified nature.

“At approximately 8 p.m. Pacific on Sunday (0300 GMT on Monday), Alaska Airlines experienced an IT outage that’s impacting our operations,” the airline noted in a prepared statement. “We requested a temporary, system-wide ground stop for Alaska and Horizon Air flights.”

The grounding affects more…