Delta Air Lines said its flights were slowly resuming after a system outage caused flight delays and cancellations Sunday evening.
About 150 flights were canceled, with more cancellations expected, according to Delta.
In a sign that effects on travelers could continue, Delta is also waiving change fees for travelers with flights scheduled through Monday.
“I want to apologize to all of our customers who have been impacted by this frustrating situation,” said Delta CEO Ed Bastian in a written statement. “This type of disruption is not acceptable to the Delta family who prides itself on reliability and customer service. I also want to thank our employees who are working tirelessly to accommodate our customers.”
Delta said at 11:45 p.m. it had lifted the ground stop. The outage was first reported around 7:15 p.m.
Flights from Atlanta to some cities had been halted unti 11:30 p.m. Exacerbating the issue, Delta said not all the delays and cancellations were reflected through reservations agents, on the Delta website, app or on airport information screens.
According to the Federal Aviation Administration's web page on airport conditions earlier in the evening, flights from Atlanta destined for Minneapolis-St. Paul International, and New York's LaGuardia Airport were not be allowed to depart until at or after 11:30 p.m.
Some arriving flights were delayed, which also affected departing flights, according to the FAA.
During the outage, Delta in a statement said "teams are expeditiously working to fix a systems outage that has resulted in departure delays and cancellations for flights on the ground. Flights in the air remain unaffected.
"Some customers are experiencing delays upon landing, particularly at Delta's hub airports," according to the airport. "Delta apologizes to customers for the inconvenience."
Delta's largest hub is in Atlanta.