British Airways said Saturday that it has canceled all of its flights from London's Heathrow and Gatwick airports for the rest of the day because of a "major IT system failure."
The airline has not indicated what is causing the computer problem, but said it has no evidence of a cyberattack.
The airline had earlier suspended flights up to 5 p.m. local time because the two airports had become severely congested.
The global computer failure has caused misery for tens of thousands of travelers on a key holiday weekend in Britain. Both airports — major hubs for worldwide travel — are overflowing with stranded, frustrated passengers.
Passengers at Heathrow reported long lines at check-in counters and the failure of the airline's website and mobile app. The airline said the problems have also affected call centers.
The airline said it's working to restore services beginning Sunday, although there will still be some disruption. It said it expects London-bound flights to land on schedule on Sunday.
8:55 a.m.: This article was updated with British Airways canceling all of its Saturday flights from London.
5:30 a.m.: This article was updated with British Airways canceling flights until 5 p.m. London time.