More than 600 flights are canceled and nearly 2,000 running late as a winter storm sweeps across the Northeast.

Adding to travelers' woes: United Airlines is experiencing problems with its passenger-service computer system.

By midday Tuesday, 350 United flights had been delayed, according to tracking service FlightAware.com. It wasn't clear how many were due to the computer outage. United didn't immediately provide details.

Snow and ice are snarling air traffic in the Northeast. At midday, more than 100 departures have been canceled at Newark Liberty Airport in New Jersey and dozens more at New York's LaGuardia Airport and in Philadelphia.

Several storms have slammed travelers this winter. Airlines have canceled more than 75,000 domestic flights since Dec. 1, the most since the government started keeping records in winter 1987-1988.

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