FlyChicago.com said 251 flights into and out of O'Hare were canceled on Christmas Eve, and 164 were canceled into and out of Midway. Arrival delays at Midway were close to two hours.
The Christmas Eve cancelations in Chicago were among more than 2,300 canceled nationwide, according to FlightAware.
The cancelations were fueled by the massive winter storm that stretched from the Great Lakes area to the Mexican border. About 60% of the U.S. population faced some sort of winter weather advisory or warning, and temperatures plummeted drastically below normal from east of the Rocky Mountains to the Appalachians, the National Weather Service said.
The Associated Press contributed to this report.