More than 370,000 homes and businesses are still without power in parts of the central and north-eastern US after a weekend ice and snow storm rolled across the region.
More than 7,000 flights were behind schedule by Monday night, many of those in New York, Washington and Chicago as people struggled to travel before Christmas.
At least 11 people have been killed in the storm.
States kept emergency shelters open for people who would be without power, some through Christmas.
About 250,000 of the people without power were in Michigan, where suppliers said it would be days before power is restored because of the difficulty of working around broken lines.
In Maine, the number of customers without power rose to more than 100,000.
Around 115,000 homes in the region were without power and some may not have it restored until after Christmas.