Thousands of passengers stranded as flights expected to resume following fire in underground power facility.
Power was restored at Atlanta's Hartsfield-Jackson International Airport late Sunday and security checkpoints re-opened at 3:30 a.m. (0830GMT).
Atlanta is a major transit hub, and more than 1,000 flights were canceled in and out of the airport Sunday, stranding thousands of passengers. Delta Air Lines, which has its largest hub in Atlanta, canceled 300 flights Monday as it seeks to rebook passengers. Most of the flights were inbound for Atlanta on Monday morning.
The airline said it plans to resume its normal flight schedule by Monday afternoon.
More than 400 flights are expected to be canceled Monday.
The blackout was caused by a fire in an underground electrical facility, according to Atlanta Mayor Kasim Reed. The fire also knocked out a backup power system for the airport that was meant to stand in for the primary system.
The fire was so intense that service crews were forced to wait before fixing the issue, according to Reed said authorities have no reason to believe the fire was intentionally created but an investigation is underway.
After earlier declaring a full ground stop, the Federal Aviation Administration the airport's air traffic control facilities are "fully operational & staffed.
"We began departure prioritization there to help accelerate recovery," the agecny added.
But fog in the area may lead to air traffic delays, it said.