Delta Air Lines (NYSE:DAL) reported flights were grounded Monday after a system outage at the company’s Atlanta hub. Delta stopped worldwide departures about 3 a.m. ET, a period that would have typically had 192 departures. Delta tweeted that its systems were “down everywhere.” Tens of thousands of people were left stranded around the globe

The outage knocked Delta’s automated check-in kiosks offline. Airport screens, the airline’s website, and smartphone apps were also affected by the meltdown. Airport flight status screens were incorrectly showing flights as being on time. Agents at ticket counters had to manually check-in many passengers and were writing out boarding passes by hand.

While systems were back online by 8:40 a.m. ET, Delta warned disruptions would continue and customers heading to the airport should expect large-scale delays and cancellations throughout the day. Monday morning is one of the busiest times for both airlines and travelers. The airline advises customers to check the status of their flight before heading to the airport.

Delta blamed an overnight power outage that impacted that its computer systems and operations, but Georgia Power disputed that assessment. Craig Bell, a spokesman for Georgia Power, said in an interview, “We believe that Delta experienced an equipment failure overnight that caused a power outage.”

Delta is waiving change fees for customers ticketed to travel this week. Delta says customers booked on Monday’s flights can make one change to their itinerary for flights no later than Friday without paying the fee. The standard change fee ranges from $200 domestically up to $500 for international itineraries. Delta is also issuing refunds for travelers whose flights were canceled or significantly delayed.

Delta operates more than 800 aircraft and employs more than 80,000 people around the world. The company has long had a reputation for punctuality and lack of cancellations. Delta CEO Ed Bastian reported during the second-quarter earnings call that the mainline airline had 77 days during April, May and June with no cancellations. In the system of nearly 6,000 daily flights, the airline had 23 days without cancellations. Delta ranks third in the world in terms of most passengers carried, serving nearly 180 million customers annually.

The Delta outage comes shortly after a similar incident with Southwest Airlines. Three weeks ago, Southwest blamed a router failure for knocking its reservations systems offline. The airline didn’t return to near-normal operations until July 25, after more than 2,300 cancellations and nearly 8,000 late flights.

Get Analysts' Upgrades and Downgrades Daily - Enter your email address below to receive a concise daily summary of analysts' upgrades, downgrades and new coverage with MarketBeat.com's FREE daily email newsletter.