Dec 18 (efe-epa).- Atlanta International Airport was resuming normal operation early Monday, hours after an outage unleashed havoc on travelers around the country, leading to hundreds of flight cancellations during one of the most hectic travel periods of the year, according to a report from Dow Jones Newswire.

The power went out at Hartsfield-Jackson _ the busiest airport in the world by passenger traffic, with an average of 275,000 passengers daily _ shortly after 1 pm Sunday, according to airport officials.

"ATL officials are working with Georgia Power to identify the cause and remedy the situation," the airport said on its Twitter account. 

Shortly before midnight, Georgia Power tweeted that power had been restored to all essential services at the airport, including all concourses and flight operations.

The outage may be linked to a fire that caused extensive damage to a Georgia Power underground electrical facility, the utility said in a press release.

The effects of the outage were likely to spill into Monday's flights, given that aircraft and crew won't be in a position to operate as scheduled and displaced passengers will need to be accommodated.

As a result of Sunday's outage, the Federal Aviation Administration ordered all flights bound for Atlanta held on the ground.

International flights bound for the airport were diverted elsewhere, according to US Customs and Border Protection.

"The cause of the incident remains under investigation," according to a message on the airport's Twitter page, posted Sunday afternoon. 

In a statement, the FAA said, "The FAA Tower can operate normally, however, departures are delayed because airport equipment in the terminals is not working."

The outage affected "all concourses and terminal buildings," according to Twitter posts from Delta Air Lines Inc., which has a major hub in Atlanta.

Delta said it canceled 900 flights on Sunday, Dow Jones added in a report supplied to EFE.

The airline said in a tweet that it expected to operate a nearly full schedule on Monday, pending the resumption of power.

Southwest Airlines canceled all flights to or from Atlanta for the rest of the day on Sunday.

American Airlines Group Inc., the largest airline by traffic, isn't big in Atlanta.

The airline said it had 47 fights scheduled to depart Sunday from the city, 24 of which were canceled, and a similar number of arrivals.

Three arriving planes were unloaded and three planes were diverted to other airports.

This weekend marks the beginning of the hectic holiday travel season.
  

Airlines for America, a trade group, estimated that 51 million passengers would fly on US carriers globally from Dec. 15 to Jan. 4, up 3.5 percent from a year ago.

By Ian Lovett and Susan Carey