All Delta flights worldwide were grounded following a system outage on Monday morning, the airline confirmed.
In a statement posted online, Delta said: "Delta has experienced a computer outage that has affected flights scheduled for this morning. Flights awaiting departure are currently delayed.
"Flights en route are operating normally. Delta is advising travelers to check the status of their flights this morning while the issue is being addressed."
The flights were grounded due to a power outage in Atlanta which impacted Delta's computer systems at about 5 a.m.
By 8.40 a.m. some flights had resumed but Delta warned travelers cancellations and delays would continue.
Delta has published a waiver for customers traveling between today and August 12.
But people are not happy.
@Delta could you please sort your planes out, I have my own wedding to get to!
@Delta @nj1015 How do check the status of flights when the computers are down and nothing is updating reflecting all flights "on time"???
#Delta mess
Hey @Delta your website and app are not working! How do we check status of flight #deltafail AGAIN
If you're having a bad Monday, just think. You aren't Delta. You didn't have to ground all your flights around the world