Washington, Dec 18 (IANS): A power failure at the world's busiest airport, Atlanta's Hartsfield-Jackson International Airport, has crippled air traffic, forcing the cancellation of more than 1,150 departing or arriving flights and stranding thousands of travellers in the US just as people begin the busy Christmas travel week.

Officials said that the power outage at the airport started on Sunday with a fire in a Georgia Power underground electrical facility causing extensive damage, the New York Times reported.

The power failure sent a ripple of disruptions across the US, affecting flights in Chicago, Los Angeles and elsewhere. There were signs the problems would linger into Monday as Delta Air Lines announced on Sunday evening that it planned to cancel 300 flights the next day.

Three major airlines -- American, Southwest and United -- cancelled arrivals and departures at the airport on Sunday as a result of the power outage. Travellers were encouraged to check with their airlines before heading to the airport on Monday.

Many flights in the air were diverted when the power went out and the US Customs and Border Protection said on Twitter that international flights destined for Atlanta were rerouted to other airports.

The airport is the busiest in the world for passenger traffic, serving more than 104 million passengers last year, according to Airports Council International. The failure affected at least 30,000 people, airport officials said.

There were reports that some planes sat on the tarmac for more than six hours waiting to move. Earlier in the night, after more than six hours, power had been restored in one of the seven concourses.

Passengers waited in long lines on Sunday to catch taxis and public transportation. With no announcement system working and few uniformed airline employees available, passengers said they did not know whether they should stay at the airport or how and when they could reschedule their flights.

In one video, passengers at an airport terminal were seen sitting in the dark and using flashlights on their phones to see where they were going.

"There were a few emergency lights on, but it was really dark -- felt totally apocalyptic," said passenger Heather Kerwin.

Airlines cancelled more than 1,150 flights into or out of Atlanta, according to FlightAware, the flight data website.

Hartsfield-Jackson Airport handles 2,500 flights and an average of 275,000 passengers daily, according to its website.