A massive winter storm set the stage for a brutal travel day Sunday, with airlines warning of widespread cancellations and delays at some of the nation's busiest airports.RELATED STORY | Winter weather travel guide: Refunds, reb ooking, and survival tipsWidespread snow, sleet and freezing rain threatened nearly 180 million people more than half the U.S. population in a path stretching from the southern Rocky Mountains to New England, the National Weather Service said Saturday night. After sweeping through the South, forecasters said the storm was expected to move into the Northeast, dumping about 1 to 2 feet (30 to 60 centimeters) of snow from Washington through New York and Boston.More than 14,100 flights have been canceled across the U.S. since Saturday, according to flight-tracking site FlightAware. Over 10,000 of those were scheduled for Sunday.Ronald Reagan Washington National Airport warned travelers on its website of widespread flight cancellations. Nearly all of its departing flights scheduled for the day 420 flights, or 99% have been canceled.WATCH | Millions braced for winter storm forecast to spread across much of the US Significant disruptions have hit major airport hubs in Dallas-Fort Worth, Charlotte, Philadelphia and Atlanta, home to the nations busiest airport, as well as New Yorks John F. Kennedy International Airport and LaGuardia Airport.American Airlines had canceled over 1,400 flights for Sunday, about 45% of its scheduled flights for Sunday, according to FlightAware. Delta Air Lines and Southwest Airlines each reported over 1,200 cancellations for the day, while United Airlines had more than 860. JetBlue had more than 570 canceled flights, accounting for roughly 71% of its schedule for the day. ...read more read less