Photo: The Canadian Press

While power has been restored to the world's busiest airport, the travel woes will linger for days.

Thousands of people were stranded Monday morning at Hartsfield-Jackson Atlanta International Airport, where more than 1,000 flights were grounded just days before the start of the Christmas travel rush.

A sudden power outage that Georgia Power said was caused by a fire in an underground electrical facility brought the airport to a standstill Sunday about 1 p.m.

All outgoing flights were halted, and arriving planes were held on the ground at their point of departure. International flights were being diverted, officials said.

Delta Air Lines, with its biggest hub in Atlanta, will be hardest hit. By Sunday evening, Delta had already cancelled nearly 900 flights and another 300 Monday, nearly all of them in Atlanta, according to tracking service FlightAware.com.

Robert Mann, an aviation consultant and former American Airlines executive, said it likely will be Tuesday before Delta's operations in Atlanta return to normal, and for passengers "it could be most of the week" because there aren't many open seats on other flights in the last week before Christmas.

One bit of good news, according to Mann: Delta has more spare planes and available crews in Atlanta than anywhere else, which should help it to recover.

Delta customers flying to or from Atlanta can make a one-time change to travel plans without incurring a $200 change fee. The airline also encouraged travellers not to pick up their bags Monday because of anticipated congestion at the airport.

Still, when flights at Atlanta were grounded for most of one day last spring, it took Delta five days — and about 4,000 cancelled flights — before it fully recovered.

Like Sunday's outage, that April storm hit Delta's largest hub at a busy travel time when there weren't many empty seats to accommodate customers from cancelled flights. At the time, CEO Ed Bastian vowed Delta would make "significant improvements" to its system for scheduling and tracking aircraft crews to recover more quickly from disruptions.

Other airlines also cancelled flights for the rest of Sunday. American Airlines cancelled 24 departures and an equal number of arrivals, said spokesman Ross Feinstein. The airline also diverted three planes that were headed to Atlanta when the outage struck, sending them instead to Dallas, Nashville and back to Philadelphia.

The city of Atlanta provided shuttle service to the Georgia Convention Center on Sunday for travellers needing a place to stay.

Delta passenger Emilia Duca, 32, was on her way to Wisconsin from Bogota, Colombia, when she got stuck in Atlanta. She said police made passengers who were in the baggage claim area move to a higher floor. She said restaurants and shops were closed. Vending machines weren't working.

"A lot of people are arriving, and no one is going out. No one is saying anything official. We are stuck here," she said. "It's a nightmare."

Some passengers said there was a lack of information from airport officials and little help from first responders to get the disabled and the elderly through the airport without the use of escalators and elevators.