Airline passengers wait in front of a Turkish Airlines plane at the Hartsfield-Jackson Atlanta International Airport in Atlanta, Georgia.

Operations were returning to normal at Atlanta's Hartsfield-Jackson International Airport on Tuesday in the wake of a massive blackout over the weekend that grounded hundreds of flights and stranded thousands of passengers.

Only six flights were canceled into or out of the airport on Tuesday, according to flight-tracking website FlightAware. Atlanta, the world's busiest airport, is a major connection point that handles some 2,500 flights and 275,000 passengers a day.

Airlines — including Delta, which is headquartered in Atlanta, and Southwest — scrubbed more than 1,000 flights on Sunday after a fire shut down power to the airport. The outage knocked out jet bridges, which are used to board and unload passengers; airport screens and concession stands, among other things.

Delta said it would reimburse travelers who needed to stay at hotels on Sunday.

Travelers stranded in the crippling outage were left to play a massive game of musical chairs to secure seats on other flights.

During bad weather or other foreseen events, airlines often give travelers plenty of time to rebook their flights for other dates, a way to avoid chaos at the airport, long before a snowflake falls or tropical-storm winds pick up. But because the blackout was sudden airlines had no time to prepare for the influx of stranded travelers.

Delta said it added a "handful" of flights on Monday to accommodate travelers. However, some passengers were offered flights scheduled for midweek.

Carriers waived date-change and fare-difference fees so passengers could rebook for other dates. Delta said travelers stuck in the blackout could rebook for travel as late as Friday.

Some passengers took to social media to complain that they couldn't get seats until Wednesday, three days after the blackout. Some were asking the airline to cancel and refund their trips altogether because it was too late for them to travel.

The blackout's timing came at the start of a busy holiday travel week, which is a tough time to get a seat in general.

One piece of good news: Business travel tends to slow down in the days before Christmas, and some travelers flying for work are likely to have called off trips booked for early in the week because of the chaos in Atlanta, said Henry Harteveldt, travel industry analyst and founder of consulting firm Atmosphere Research Group.

One challenge is that after years of mergers between U.S. carriers that gave birth to mega-sized airlines, agreements between competitors to rebook passengers on rival airlines have been dying out, he added.

"You have to view this as a multidimensional game of chess," he said.