Workers are being brought in from the Midwest and Florida to help in the storm's aftermath, it said.
Hurricane Florence's leading edge battered the Carolina coast Thursday, bending trees and shooting frothy sea water over streets on the Outer Banks, as the hulking storm closed in with 105 miles per hour winds for a drenching siege that could last all weekend.
It is now heading towards the US East Coast that it is predicted to hit on Friday.
FlightAware said in its midday report Thursday that the number of canceled flights is relatively small and could increase.
Ryan Maue, a meteorologist with weathermodels.com, warns that up to 10 trillion gallons of rain could fall on North Carolina from Florence.
Hurricane-force winds were blowing 80 miles from its centre, and tropical storm force winds reached up to 195 miles from the eye. Overall, Florence is about 400 miles wide.
Georgia Governor Nathan Deal declared a state of emergency "in light of the storm's forecasted southward track after making landfall". "This storm is extremely risky".
About 1.7 million people in North Carolina, South Carolina and Virginia are under voluntary or mandatory evacuation orders and millions of others live in areas likely to be affected by what officials called a "once in a lifetime" storm.
Airlines cancelled almost 1,000 flights with more cancellations to come. The power companies expect millions of people to be without power for days.
Life-threatening storm surge will occur near landfall and for some time after. Cloud cover that could encompass multiple states.
Hurricane Florence in the Atlantic Ocean as it threatens the US East Coast.
Waves crash around the Oceana Pier as the outer edges of Hurricane Florence being to affect the coast in Atlantic Beach on Thursday.
Warning the 10 million residents of America's Southeastern coast about Hurricane Florence, US President Donald Trump has said, "Don't play games with it". Puerto Rico and the Virgin Islands face possible isolated amounts of 3 inches. He claimed the numbers were inflated by Democrats that were "trying to make [him] look bad".
Florence is headed straight for some of the most well-known military bases in the country. Helene was weakening, however, and posed no danger to land, the NHC said, while Isaac could bring heavy rain to Martinique, Dominica and Guadeloupe. "From the storm surge alone, tens of thousands of structures are expected to be flooded in North Carolina". The losses won't be easily or quickly overcome. This is bigger than both of the Carolinas and THIS is why rain is the biggest issue. There are now fewer tourists to send away.
It's unclear exactly how many people fled, but more than 1.7 million people in the Carolinas and Virginia were warned to clear out.
Florence's heavy rains could cause an environmental disaster if waste from hog manure pits, coal ash dumps and other industrial sites wash into homes or threaten drinking water supplies.
Once a Category 4 hurricane with winds of 140 miles per hour (225 kph), the hurricane was downgraded to a Category 1 on Thursday night. We are more inland from the coast. "It's a big one", he said at the White House. "We have two boats and all our worldly possessions", said Susan Patchkofsky, who refused her family's pleas to evacuate and stayed at Emerald Isle with her husband. He says: "If Mama and Grandma are going, then a lot of people are leaving". "Be ready to move to the safest place inside your shelter if necessary".
What would you take if a major hurricane was threatening to inundate or pull apart your home? "At this time, we are fully focused on preparing for, responding to, and recovering from Hurricane Florence and the storms in the Pacific", DHS press secretary Tyler Houlton told Politico in a statement.