UPDATE:  A power outage brought the world's busiest airport to a standstill Sunday, ruining holiday travel for thousands and threatening another day of headaches, with hundreds of flights on Monday already canceled.

Hartsfield-Jackson International Airport in Atlanta lost power shortly after 1 p.m. ET on Sunday, leaving passengers trapped inside airport terminals and some in planes on the tarmac for hours.

By late Sunday, the airport had canceled 1,173 flights and delayed 207, according to FlightAware.com. Delta Air Lines, which is headquartered in Atlanta, said it was canceling another 300 flights, mostly to Atlanta, on Monday.

UPDATE: Delta flights departing to and coming from Atlanta have been canceled at the Chattanooga Airport.

Channel 3 spoke with a spokesperson for the Chattanooga Airport.

Here is what they said:

“Due to some power outages at Atlanta’s Hartsville-Jackson International Airport, Delta flights from Chattanooga to Atlanta and from Atlanta to Chattanooga have been canceled. We have no further information at this time and as always we ask that you check with your air carrier before arriving at the  airport for your flight.”

If you are flying with a different airline, you can check the status of your flight here.

PREVIOUS STORY: Flights headed to Atlanta are being impacted by the outage. 

The airport tweeted that the FAA has put a ground-stop on all flights headed to Hartsfield-Jackson International Airport.

Several flights out of Chattanooga are being affected.  You can check the status of your flight using the CHA flight tracker on WRCBtv.com.

PREVIOUS STORY: Power went out at Atlanta's Hartsfield-Jackson International Airport early Sunday afternoon.

Airport officials say the outage occurred at 12:55 p.m., and affects several areas of the airport. The outage was due to an electrical issue at a Georgia Power substation, according to an airport spokesperson who spoke to NBC News.

11 Alive's Faith Abubey was in the North Terminal at the time of the outage, and reports that all power is out there. In speaking to staff at the United Airlines desk, she says she was told that the outage was over the entire airport and that flights were grounded.

Abubey reports that the Plane Train, which connects each of the terminals below ground, is also affected.

Additionally, data service in and around the airport area is affected, limiting cell phone service in that area.

READ MORE FROM NBC ATLANTA | Power outage reported at Hartsfield-Jackson