Chicago - The winter storm bearing down on the Midwest and Northeast is causing delays and cancellations at some of the US's busiest airports. As of Thursday afternoon, nearly 2 000 flights have been grounded because of the weather.Smarter Travel reports data from FlightAware shows more than 5 00 flights have been delayed and more than 1 831 were canceled, the bulk of them arriving at or departing from airports in the Midwest and Northeast. Chicago O'Hare, Newark Liberty, LaGuardia, Cleveland-Hopkins, and Philadelphia International are seeing the more significant flight-schedule disruptions.AdvertisementTravelers have been advised to prepare for further delays and cancellations at airports throughout the weekend as the after effects of the flight groundings and cancellations will have a knock-on effect, even after the storm has passed. Passengers affected should contact their specific airlines to make use of the change-fee waivers being offered - which allows for itinerary adjustments without penalty. With most of the airlines, the waivers are available for those traveling January 1 through 3.