LONDON, Reuters, May 27, 2017 – British Airways canceled all its flights from London’s two biggest airports on Saturday after a global computer system failure caused confusion and chaos, with thousands of passengers queuing for hours and planes left stuck on runways.

FILE PHOTO – British Airways logos are seen on tailfins at Heathrow Airport in west London, Britain May 12, 2011.

The airline, which said there was no evidence of a cyber attack, said the major outage meant it had been forced to cancel all scheduled flights from Heathrow and Gatwick and had also hit its call centers and website.

“Most long-haul flights due to land in London tomorrow are expected to arrive as normal, and we are working to restore our services from tomorrow, although some delays and disruption may continue into Sunday,” said BA, part of Europe’s largest airline group IAG.

“We are extremely sorry for the inconvenience this is causing our customers during this busy holiday period.”

People wait with their luggage at Heathrow Terminal 5 in London , Britain May 27, 2017.

The problems, which passengers said had affected flights across Britain, came on a particularly busy weekend with a public holiday on Monday and many children starting their school half-term breaks.

Terminals at Heathrow and Gatwick became jammed with angry passengers, with confused BA staff unable to help as they had no access to their computers.

“It’s a complete nightmare. There’s just hundreds and thousands of people accumulating in the departures bit,” Roshni Burt, who was flying from Heathrow to Bahrain with her young son, told Reuters.

She arrived at the airport at 0730 GMT, queued for hours at the check-in, where the baggage drop-off system stopped working, and then waited at the departure gate for two hours until passengers were told the flight was canceled.

All the affected passengers were corralled through a single gate so they could go back through border checks and then re-book flights