Traffic along southbound Interstate 25 slows during heavy snow and high winds at Thornton, Colorado, near Denver, on Thursday. Up to 8 inches of new snow were expected in Denver, which set a record for its snowiest Christmas with the nearly 8 inches that fell Tuesday. United canceled 168 flights nationwide Thursday mostly because of the weather in Denver, its second-largest hub, to help prevent planes from being stranded there. That's about 5 percent of the airline's daily schedule.