UPDATE May 28 at 3:22 p.m. EST:
British Airways announced Sunday that it is resuming departures from London's Heathrow and Gatwick airports.
This comes after a worldwide computer outage halted flights Saturday.
"We're extremely sorry for the disruption caused to you," the airline posted on its Facebook page. "Work continues to restore all of our IT systems but we expect some further disruption today."
BREAKING: British Airways cancels London Heathrow and Gatwick flights for rest of Saturday because of major tech failure.— The Associated Press (@AP) May 27, 2017
UPDATE 11:54 a.m.: BA has cancelled all flights for the rest of Saturday.
ORIGINAL STORY: Air travelers faced delays Saturday because of a worldwide computer systems failure at British Airways, the airline said.
BA apologized in a statement for what it called an "IT systems outage" and said it was working to resolve the problem.
BA said in a tweet in a tweet that the problem is global.
Passengers at Heathrow Airport reported long lines at check-in counters and flight delays.
More footage from inside the airport.
One posted a picture on Twitter of people stuck on the tarmac.
"We've tried all of the self-check-in machines. None were working, apart from one," said Terry Page, booked on a flight to Texas. "There was a huge queue for it and it later transpired that it didn't actually work, but you didn't discover that until you got to the front."
Another traveler, PR executive Melissa Davis, said she was held for more than an hour and a half on the tarmac at Heathrow aboard a BA flight arriving from Belfast.
She said passengers had been told they could not transfer to other flights because "they can't bring up our details." Heathrow said the IT problem had caused "some delays for passengers" and it was working with BA to resolve it.
The problem comes on a holiday weekend, when thousands of Britons are travelling. BA passengers were hit with severe delays in July and September 2016 because of problems with the airline's online check-in systems.
--The Associated Press contributed to this report.