BBC News Channel

British Airways passenger Dan Power was meant to be on a plane to Milan with his 80 year-old grandmother,

But he's stuck at Heathrow. He told BBC News his main concern was that his grandmother might have to sleep on the airport terminal floor overnight.

Here's some background information on British Airways:

• Passengers transported in 2016: 44m, average 120,000 per day.

• BA flies to 113 countries around the world.
• British Airways is part of the larger International Airlines Group, alongside sister airlines Iberia, Vueling and Aer Lingus.
• IAG was ranked the 6th largest carrier in the world in terms of revenue.

Passenger Tim Reid describes the scenes at the airport.

If your flight departed from within the European Union or was with a European airline, you might have rights under EU law to claim if the delay or cancellation was within the airline's control.

• Short-haul flights: 250 euros for delays of more than three hours
• Medium-haul flights: 400 euros for delays of more than three hours
• Long-haul flights: 300 euros for delays of between three and four hours; and 600 euros for delays of more than four hours
• If your flight's delayed for two or more hours the airline must offer food and drink, access to phone calls and emails, and accommodation if you're delayed overnight - including transfers between the airport and the hotel

BBC Politics reporter Gavin Stamp is at Gatwick Airport where he was planning to travel to Jersey on holiday.

Here's what he said:

"I'm stuck at Gatwick along with thousands of other BA passengers.

"People are being told to go home and are being given forms setting out what compensation is on offer for hotels.

"The picture is totally confused as you can't rebook at the moment. But given that thousands of people are effectively marooned, the mood is relatively calm considering."

The airline says it has no evidence at this stage to suggest a cyber attack.

Image source, @TIMREIDCE

British Airways has cancelled all flights from Heathrow and Gatwick until 18:00 BST because of computer problems.

A "major IT system failure that is causing very severe disruption to our flight operations worldwide", the airline said.

It apologised for the "global system outage" and said it was "working to resolve the the problem".

Heathrow Airport said it was "working closely" with BA to solve the issue.

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British Airways has issued a full statement after an IT failure caused mass cancellations of flights out of London airports:

"We have experienced a major IT system failure that is causing very severe disruption to our flight operations worldwide.

"The terminals at Heathrow and Gatwick have become extremely congested and we have cancelled all flights from Heathrow and Gatwick before 6pm UK time today, so please do not come to the airports.

"We will provide more information on ba.com, Twitter and through airport communication channels as soon as we can for flights due to depart after that time.

"We will be updating the situation via the media regularly throughout the day.

"We are extremely sorry for the inconvenience this is causing our customers and we are working to resolve the situation as quickly as possible."

The airline said the terminals at Heathrow and Gatwick airports had "become extremely congested" and that all flights before 18:00 BST are cancelled.

A BA spokesperson said: "Please do not come to the airports."

• All British Airways flights scheduled to depart from London Heathrow and Gatwick airports before 18:00 BST are cancelled
• British Airways passengers around the world are facing long delays
• Domestic and international flights are affected
• A BA captain has said the failure affects the passenger and baggage manifests
• Check in, bag drop, take-offs and landings are all delayed as Heathrow Airport faces a logjam of delayed flights blocking gates
• Heathrow Airport advises passengers to check the status of their flights before travelling to the airport