LONDON (AP) — The Latest on British Airways flight stalled by IT failure (all times local):

1:20 p.m.

British Airways has canceled all flights from London's Heathrow and Gatwick airports as a global IT failure causes severe disruption for travelers.

The airline says it has suffered a "major IT systems failure."

BA says terminals at Heathrow and Gatwick have become extremely congested and it is cancelling all flights from the airports until 6 p.m. (1700GMT). It is urging passengers not to go to the airports.

Earlier, passengers at Heathrow reported long lines at check-in counters and flight delays.

BA has not said what is causing the computer problem, but says it is working to resolve it as quickly as possible.

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12:10 p.m.

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. It said in a tweet that the problem is global.

Passengers at Heathrow Airport reported long lines at check-in counters and flight delays. One posted a picture on Twitter of BA staff writing gate numbers on a white board.

"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."

The problem comes on a holiday weekend, when thousands of Britons are travelling.