More than 2,000 flights have already been affected.

A massive power outage at Hartsfield-Jackson Atlanta International Airport — the busiest airport in the U.S. — wreaked havoc on Sunday just as holiday travel was ramping up.

Although the FAA suspended incoming flights, it was too late for passengers and crew on planes on the runways and taxiways. In some cases, passengers were stuck on planes for as many as seven hours.

CNN reporter Betsy Klein was one such passenger, and she detailed her experience over the several hours it took to finally get off her flight.

Among the many problems facing airport and flight crews at Hartsfield-Jackson: Without power, there were only five sets of stairs available to deplane dozens of flights, a Delta pilot told passengers on Klein's flight.

According to Atlanta Mayor Kasim Reed, the outage was caused by an underground electrical fire, the Atlanta Journal-Constitution reported. CNN additionally reported that the fire also destroyed the system that should have been the backup source of power for the airport.

It wasn't until after 10 p.m. that Mayor Reed tweeted that all passengers had been deplaned.

Upon finally getting to the airport, Klein described Hartsfield-Jackson as a “war zone.”

“Hartsfield looks like a war zone” Klein tweeted. “People sleeping on the floor, fighting mostly civilly over outlets, elderly people and small children struggling with stairs.”

Power has been restored to some terminals, but may not be fully restored until midnight.

The City of Atlanta is offering shuttles to the Georgia International Convention Center for those in need of accommodations for the night.

More than 1,150 flights in and out of Atlanta were canceled on Sunday, according to FlightAware. Hartsfield-Jackson handles upwards of 300,000 passengers each day.

Delta Air Lines has canceled at least 300 flights scheduled for Monday as a result of the outage, the Atlanta Journal-Constitution reported.

Since Atlanta is a major hub, delays and cancelations could ripple throughout the country this week. Even if Atlanta isn't on your itinerary, if you're traveling this week — like the millions of other Americans on the move this holiday season — check with your airline for updated flight status.