Washington - Snowfall in the northeastern United States caused flight cancellations and airport delays on Tuesday while federal government offices and schools closed due to the foul weather.Major delays were reported at airports in Newark, New Jersey, as well as further south in Philadelphia, according to the FlightAware website.Snow and ice were also slowing air traffic at New York's LaGuardia and John F Kennedy International airports.With a winter storm warning in effect, authorities at the US capital's Reagan National and Dulles International airports urged passengers to check the status of their flights before heading out the door."Some airlines have begun issuing weather related cancellations. Further cancellations and delays are likely throughout the morning," said a notice from the Metropolitan Washington Airports Authority. According to forecasts, the snow was expected to intensify in Washington and the neighbouring states of Maryland and Virginia over the course of the morning before tapering off in the afternoon.In Washington, the federal government operated at a slower pace as agencies closed to keep commuters off roads and prevent accidents. Schools across the region were also shut.