Airports throughout the Mid-Atlantic began operating again Thursday after a blizzard tore up the East Coast, shutting down runways for the second time in less than a week and causing one of the biggest disruptions to air travel since the 9/11 hijackings, according to airlines and government statistics.

Ground transportation throughout the region remains slow to recover causing many businesses and federal agencies to remain closed for the day.

Residents throughout the region started digging out as cities rushed to clear snow-covered streets and utility crews worked to restore power to thousands of customers.

Schools were closed for the rest of the week and in many cities and in Washington, D.C., the federal government was shut down for the fourth day in a row.

D.C. Mayor Adrian Fenty said it would take another 24 hours to see a lot of normal government operations.

Airports in Washington, Baltimore, Philadelphia and Newark shut down by heavy snow and high winds - had resumed Thursday morning on a limited basis. At least 5,700 flights were canceled on Wednesday alone, according to a USA TODAY survey of carriers.

Airlines say they expect to cancel more than 1,000 flights Thursday. By comparison, airlines canceled 2,700 flights in all of November, according to the federal Bureau of Transportation Statistics.

Flights began to arrive Thursday morning at Dulles International Airport in Washington, D.C. Both of Baltimore-Washington International Thurgood Marshall Airport's two main runways reopened, but officials warned that flight cancellations would continue through the morning because of the storm.

One primary runway was open at Philadelphia International Airport on Thursday morning and a second should open by 9 a.m., said airport spokeswoman Victoria Lupica.

Crews have been working to clear runways and taxiways around the clock and airlines are resuming limited schedules of flights in and out of Philadelphia. Officials expect the airlines to cancel some scheduled flights but conditions are fine for flying in Philadelphia, Lupica said.

Officials at Washington's Reagan National Airport said they hope to have at least some flights going there by early Thursday afternoon.

The storm was "paralyzing to air transportation in the country," said David Castelveter, spokesman for the airline trade group, the Air Transport Association. It will take days for a final tally, but the storms probably caused one of the biggest impacts on air travel in a decade, Castelveter said.

Airlines made the deep cuts in their schedules in an attempt to keep jets and passengers from becoming stranded. Thousands of flights were grounded last weekend by a storm that hammered Washington, D.C., and Baltimore.

This week's storm that enveloped the East Coast from Virginia to Cape Cod also caused significant delays and cancellations at New York City's John F. Kennedy International and La Guardia airports, according to FlightStats, a flight-tracking company.

US Airways had the most cancellations, nearly 1,700 out of its 3,060 departures, spokeswoman Valerie Wunder said. Delta Air Lines grounded 960 flights, spokesman Trebor Banstetter said.

The snow has disrupted everyone from travelers to people just trying to get through the day.