FAA website has it listed as a ground stop.
From fly.faa.gov/ois:
MESSAGE: EVENT TIME: 22/2345 - 0100
GROUND STOP ALL UAL MAINLINE DEPARTURES TO DOMESTIC DESTINATIONS.
INTERNATIONAL DESTINATIONS ARE EXEMPT. UAL SUB CARRIERS ARE EXEMPT.
UPDATE AT 0100Z. THIS IS UAL REQUEST
EFFECTIVE TIME: 222342 - 230130
SIGNATURE: 17/01/22 23:42