British Airways has restarted flights from Heathrow and Gatwick which were earlier cancelled due to computer problems.
The airline had assured passengers that there was no evidence of a cyber-attack, but did not disclose the cause of the disruption.
Passengers on one flight were told by the pilot that the IT problems were “catastrophic”, and should not come to the airports,” according to UK Guardian.
“Following the major IT system failure experienced earlier today, with regret we have had to cancel all flights leaving from Heathrow and Gatwick for the rest of Saturday,” a spokeswoman said.
“We are working hard to get our customers who were due to fly today on to the next available flights over the course of the rest of the weekend.
“Those unable to fly will be offered a full refund.
“The system outage has also affected our call centres and our website but we will update customers as soon as we are able to.”
All passengers affected by the failure were offered the option of rescheduling or a refund.
Other airlines flying in and out of Heathrow and Gatwick, though, were not affected.