WASHINGTON - Airlines cancelled over 4,400 US flights on Friday as a massive winter storm snarled airport operations around the United States and frustrated thousands of holiday travellers.

The cancellations followed nearly 2,700 cancelled flights on Thursday, according to flight tracking website FlightAware.

Passenger railroad Amtrak has cancelled dozens of trains through Christmas, disrupting holiday travel for thousands.

The Federal Aviation Administration (FAA) imposed ground stops or delays for de-icing at a number of US airports because of winter weather.

It said “severe winter weather moving across the Great Lakes into the Northeast will have a major impact” on flights, adding that “flight delays are likely from Boston to DC Metropolitan area airports, Seattle-Tacoma and Portland International Airports and Aspen” in Colorado.

Transportation Secretary Pete Buttigieg told CNN the US aviation system “is operating under enormous strain” and two different storms and high winds are affecting airports around the country.

About 10 per cent of US flights were cancelled on Thursday, Mr Buttigieg said.

“You are going to see a lot of disruption,” he said.

Seattle-Tacoma International Airport had 44 per cent of departing flights cancelled as of 11am PST (10pm Singapore time). The FAA early on Friday issued a ground stop there due to snow and ice.

More than 40 per cent of departing flights at Detroit Metro were cancelled, 60 per cent at Portland, 34 per cent at New York’s LaGuardia, 27 per cent at Boston and 21 per cent at Chicago O’Hare, which noted that wind gusts of up to 80kmh are expected in Chicago on Friday.

Another 5,500 US flights were delayed on Friday - including more than a fifth of those operated by American Airlines, United Airlines, Delta Air Lines and Southwest Airlines.

Southwest cancelled 889 flights on Friday, more than one-fifth of all its scheduled flights, while Alaska Airlines canceled 359, or 46 per cent, of its flights. REUTERS