The world's busiest airport, in the US city of Atlanta, said early Monday that power had been restored after an outage left passengers in the dark and affected hundreds of flights.

"Power has been restored on all concourses," the Hartsfield-Jackson Atlanta International Airport said on its Twitter account, about 11 hours after first reporting a power disruption.

Giving an idea of how many people were affected, the airport added: "5,000+ meals are being delivered to passengers. Trains will be operational soon