A major power outage halted air traffic Sunday at Hartsfield-Jackson Atlanta International Airport, the world's busiest. Hundreds of thousands of travelers worldwide were affected.
The power in some areas of the airport was restored late Sunday and Georgia Power said it expected all of it to be back on by midnight.
"Georgia Power believes the issue may have involved a fire which caused extensive damage in a Georgia Power underground electrical facility. The fire was safely extinguished by fire crews before Georgia Power could enter the area to assess damage and begin repairs," the utility said in a statement.
The FAA said it ordered a ground stop for flights into the airport due to the impact of the outage on airport terminals. A ground stop means flights to the airport are held at departure airports across the nation. The Federal Aviation Administration said departures also were delayed.
"The FAA tower can operate normally, however, departures are delayed because airport equipment in the terminals is not working," the agency said in a statement.
The flight-tracking website FlightAware said inbound flights were being held at their departure airports until 4 p.m. ET Flight delays out of the airport averaged 1 hour and 40 minutes, the website said.
Airport officials said the outage began just before 1 p.m. Georgia Power said it was aware of the outage and was investigating.
U.S. Customs and Border Protection announced that international flights were being diverted to other airports.
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Many major airlines canceled flights and Southwest said "all but a handful of international flights" were canceled.
In 2016, the Atlanta airport handled 104,171,935 passengers, the most of any airport in the world.