(CNN) -- Air traffic is returning to its regular busy pace at Hartsfield-Jackson International Airport in Atlanta, Georgia, hours after a power outage forced Delta Airlines to cancel or delay flights on Monday.
"The power is back on and operations are returning to normal," said airport spokeswoman Katena Carvajales.
The power outage began Sunday evening, as many people were trekking back home after the Thanksgiving holiday.
It affected 18 gates in Concourse B, at one point prompting Delta to request a full ground stop, said FAA spokeswoman Kathleen Bergen.
About two dozen flights were canceled, said Anthony Black, a spokesman for the airline.
The ground stop later changed to a ground delay, which meant the Delta concourses could accept about 40 arrivals an hour. Still, many flights were delayed by up to an hour as the airline moved flights around to other gates.
Delta is working with the airport to determine the cause of the outage, Black said.