A powerful winter storm sweeping the U.S. East Coast shut down the vast majority of flights out of the region’s largest airports on February 23, including in the New York area and in Boston.

More than 5,300 flights in, out or within the U.S. were scrapped at the start of the week, according to FlightAware as of 2 a.m. New York time February 23. The impact on the region’s airports are at least as severe as the late-January winter storms.

Major snowfall of as much as 30 inches is expected across the East Coast in some areas, with the heaviest set through the night of February 22, and into the morning of February 23, the National Weather Service said, making travel impossible.

Airports including LaGuardia in New York have canceled 98% of flights, while the John F. Kennedy hub halted 88% of operations. Boston Logan saw 93% of scheduled services scrapped, and Philadelphia suspended 83% of services.

Delta Air Lines Inc. said earlier that it expected to halt operations at LaGuardia, JFK and Boston Logan into February 24, while warning of broader disruption across the east coast.

Airport operations urged passengers to confirm with airlines of their flight status before traveling to the airport.