Updated

Hundreds of flights have been canceled for Monday after a massive power outage at the Hartsfield-Jackson Atlanta International Airport snarled air travel throughout the country a day earlier.

A statement on Delta’s website confirmed that nearly 1,000 flights were cancelled on Sunday and that an additional 300 flights were canceled for Monday “to give the operation there an opportunity to more quickly return to normal.”Delta runs a large operation in Atlanta, making it the airline’s busiest hub, USA Today reported.

The power outage affected the entire airport on Sunday afternoon and was restored later that night. Georgia Power told The Atlanta Journal-Constitution that it believes a failure of its equipment may have started the fire.

“Georgia Power's system responded properly by isolating areas where equipment wasn't operating correctly to ensure safety and minimize damage,” the company told the paper. “No personnel or passengers were in danger at any time.”

Southwest Airlines, the second busiest carrier there, said it cancelled "all remaining operations" for the day but that operations should return to normal by Monday.

An American Airlines spokesperson said three of the carrier's flights have been diverted and there have been "a couple of cancelations."

Robert Mann, an aviation consultant and former American Airlines executive, said it will likely be Tuesday before Delta's operations in Atlanta return to normal, Daily Mail reported.

According to FlightAware.com, 1,174 flights have been canceled at Hartsfield-Jackson as of 9:30 p.m. ET on Sunday.

Kasim Reed, the city’s mayor, took to twitter late Sunday night to announce that power had been fully restored but not before the outage had managed to ground all outgoing flights and halt any incoming.

Reed told news outlets at a press conference Sunday evening airlines are working to rebook flights, and said that a fire caused the power outage and produced potentially toxic fumes, which took two hours for fire crews to put out. Reed said it remains unclear how the fire started but it will be investigated.

Almost 2,500 planes arrive and depart Hartsfield-Jackson Atlanta International daily, and the airport averages 275,000 passengers per day, according to the airport's website.

Fox News’ Nicole Darrah, Alexandra Deabler and The Associated Press contributed to this report.