DENVER, Colorado (AP) -- United Airlines, hit hard by weekend storms in the Midwest, canceled dozens more flights Thursday as the second storm since Christmas threatened to pile 20 inches of new snow on Colorado. 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.