Delta Air Lines has resumed flights after a “major system-wide network outage” saw its jets grounded.
Air travellers faced long queues to check in at Heathrow on Monday after a power outage in Atlanta at 2.38am local time plunged the airline’s operations worldwide and computer systems into chaos.
The company, which operates flights out of Edinburgh, Heathrow and Manchester, has since said the “ground stop has been lifted and limited departures are resuming”.
A spokeswoman added: “Customers heading to the airport should expect delays and cancellations. While inquiries are high and wait times are long, our customer service agents are doing everything they can to assist.”
Flights across the world were affected by what the company said on Twitter was a “major system-wide network outage”.
Frustrated passengers took to social media to voice their outrage at the delays - with some reporting handwritten tickets being used by the airline.
Amanda Jackson said on Twitter: “Chaos trying to check in @Delta Heathrow t3. Been in queue for 1.5 hours. You seriously need to open more desks to overcome technical hitch.”
Peter Taylor tweeted: “Still in Heathrow - should have been on 9:40 flight to Boston - waiting for news - staff apologetic, even had the captain speak to us.”
Cassie Chou took to Instagram to share a picture of inside the airport and added a caption saying Delta staff in Heathrow were “handwriting tickets manually”.
The airline began in 1924 as an aerial crop-dusting operation called Huff Daland Dusters, and now serves more than 160 million travellers, according to its website.