Travellers are still being warned to expect "delays and cancellations" despite some flights taking off after computer problems.
Delta Airlines has said a ground stop has been lifted and a number of departures have begun following a major computer crash.
The US company has confirmed some flights are now
taking off after a power outage caused its IT systems to crash, leaving
passengers stranded at airports around the world
as scheduled flights were not taking off.
It confirmed the news on Twitter: "Delta ground stop has been lifted & limited departures resuming following power outage in ATL that impacted Delta computer systems."
In a statement, the airline said customers should still expect delays and cancellations because of the more than three hour halt caused by a computer breakdown at its hub in Atlanta.
The firm also said there may be some lag time in the display of
accurate flight status and that a travel waiver for customers travelling
today through to 12 August is in effect.
Frustrated passengers stuck in check-in queues at airports have been expressing their outrage on social media.
Jake Chen tweeted: "1 hr.+ lines @HeathrowAirport for @Delta due to system outage oldschool manual ticketing."
Amanda Jackson said: "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."
Blue Stone tweeted: "Delta lines backed up and not moving" as lines to check-in snaked through the terminal at Baltimore Washington International airport.
Customers are still being advised to check the status of their flight before heading to the airport.
A Heathrow spokesman said: "Check-in is currently operating using a
backup system and airport staff are on hand to assist any passengers
that are impacted by the delays."
A Virgin Atlantic spokeswoman said their flights were departing as normal, but that some of their customers could be "booked on a codeshare ticket" with Delta.
The spokeswoman added: "If so, customers should check the status of their flights."
The airline began in 1924 as a crop-dusting operation. It now serves nearly 180 million travellers, according to its website
It confirmed the news on Twitter: "Delta ground stop has been lifted & limited departures resuming following power outage in ATL that impacted Delta computer systems."
In a statement, the airline said customers should still expect delays and cancellations because of the more than three hour halt caused by a computer breakdown at its hub in Atlanta.
Frustrated passengers stuck in check-in queues at airports have been expressing their outrage on social media.
Jake Chen tweeted: "1 hr.+ lines @HeathrowAirport for @Delta due to system outage oldschool manual ticketing."
Blue Stone tweeted: "Delta lines backed up and not moving" as lines to check-in snaked through the terminal at Baltimore Washington International airport.
Customers are still being advised to check the status of their flight before heading to the airport.
A Virgin Atlantic spokeswoman said their flights were departing as normal, but that some of their customers could be "booked on a codeshare ticket" with Delta.
The spokeswoman added: "If so, customers should check the status of their flights."
The airline began in 1924 as a crop-dusting operation. It now serves nearly 180 million travellers, according to its website