Alaska Airlines announced Monday that its planes are flying again after having grounded them Sunday night due to an undescribed IT problem.

Alaska Airlines says it has resumed operations early Monday morning, July 21, after an IT outage caused the airline to issue a temporary ground stop.

Alaska Airlines said it has requested a ground stop for its fleet as well as for that of regional subsidiary Horizon Air amid a computer system outage Sunday night. The request to federal authorities would keep Alaska and Horizon flights out of the air until the system is returned to normal operations, Alaska said in a statement.