Power has been restored at the international airport in the southern U.S. city of Atlanta, after an outage Sunday disrupted all flights in and out of the busy hub.

Georgia Power said it believed the problems were linked to a fire that caused extensive damage to one of its underground electrical facilities as well as circuit cables that served the airport.

Hartsfield-Jackson Airport was without power for about 10 hours before crews restored power for what Georgia Power called “all essential” services, including concourses and flight operations.

Delta Airlines has its headquarters in Atlanta and canceled about 900 flights on Sunday and another 300 on Monday.

The airport is one of the busiest in the world, with more than 2,500 daily arrivals and departures, bringing more than 250,000 passengers through the airport on an average day.