Hundreds of flights have been cancelled following a power outage at Hartsfield-Hackson Atlanta International Airport on Sunday that ruined travel plans for thousands of flyers.

Just before one of the busiest travel weeks in the U.S., a sudden power loss caused by a fire at an underground electrical facility at the airport resulted in more than 1,000 flights being cancelled Sunday, and hundreds more cancelled or diverted on Monday. While power at the airport has since been restored, many flight plans have had to be changed.

As one passenger commented, "It was like a free for all when we got off, with everyone clueless. I was on the tarmac for 6.5 hours. However, the Delta staff/pilots etc were being as helpful as they could in the situation."

"Power has been restored on all concourses, 5,000+ meals are being delivered to passengers. Trains will be operational soon," the power company posted on Twitter.

Hartsfield-Jackson, which serves 104 million passengers a year, is the world's busiest airport, a distinction it has held since 1998. The airport serves an average of 275,000 passengers daily, according to its website. Nearly 2,500 planes arrive and depart every day.