Delta flights around the world were delayed this morning due to a "computer outage", the company says.
The cause of the computer disruption isunknown, though CNN reported that US officials are investigating a potential hack; Delta has said that doesn't seem to be the likelycause.
A rival USA airline, United, suffered computer glitches in May and July 2015 that temporarily grounded hundreds of flights and backed up thousands of passengers.
Anyone who rebooks for a flight that leaves after Friday could end up paying any difference in fare but won't have to pay the change fee.
About six hours into the outage, the airline said that limited flights had resumed but that there were ongoing delays and cancelations. Delta tweeted that its systems were "down everywhere". Cancellations and delays will continue. That process was moving slowly, with one customer telling NBC, "I guess it has been a long time since they used the manual process".
The airline made a statement this morning on social media, and said that all passengers should check the status of their flight before heading to the airport- however, in some airports, flights that are listed with scheduled departure times are not correct.
Passengers line up as they wait to board Delta Air Lines flights at Rome's Leonardo Da Vinci airport, Monday, Aug. 8, 2016. Roughly 1,260 flights took off as scheduled. Confirmation of the troubles came in an official account that responds to customers via Twitter.
Airline computers juggle multiple systems that must interact to control gate, reservations, ticketing, frequent fliers.
The company said travelers will be entitled to a refund if the flight is canceled or significantly delayed. Passengers at Fargo's Hector International Airport were lined up at the ticket counters Monday morning, getting the bad news as Delta jets sat silent on the tarmac outside.
Delta Air Lines canceled around 300 hundred flights Monday after its computer systems crashed, stranding thousands of passengers on a busy travel day.
A vast number of flight delays normally creates a cascading problem that affects airline traffic for days.
Georgia Power said a piece of Delta equipment failed and caused the airline's computer systems to lose power.