Video shows chaos as BA passengers are told it could take 3 hours just to leave airport

Frustrated holidaymakers told flights cannot be immediately rebooked after system failure

Thousands of British Airways passengers who have had their flights cancelled face waits of up to three hours just to leave the airport due to severe overcrowding at Heathrow and Gatwick.

The airline has cancelled all flights from the two London airports for the rest of Saturday following a global IT crash although some flights are still leaving other airports.

BA staff have told stranded passengers they cannot rebook them on later flights because the system remains down. Those in transit have been told they cannot collect their bags.

Video footage shows chaotic scenes at Heathrow as frustrated passengers demand to know what is going on and when they will be able to take alternative flights.

An announcement from BA at the west London airport informed passengers: “We need you to leave the terminal and the way to leave the terminal is through gate number A12.

“There is a queue at the moment to get through to A12 because (we) can’t let you into the arrivals’ hall because that it too busy too, but you will have to leave through gate A12.

“You will have to try and re-book online or with another airline. Our systems are not open and we are not able to re-book any of you."

The announcement continues: "There will be no availability to pick up baggage today. Unfortunately our baggage system has failed too and we are not able to retrieve any bags."

A number of planes are stuck on the tarmac at Heathrow with passengers unable to get off because all the terminal gates are currently full.

Passengers have been told not to travel to the London airports because of the "extreme congestion".

Hundreds of frustrated passengers bombarded the airline with tweets after finding they would be unable to get their flights today.

Some tried to remain positive, with one woman tweeting that she was supposed to be flying to Estonia's capital city for her hen do.

A spokeswoman for the airline said: "We have experienced a major IT system failure that is causing very severe disruption to our flight operations worldwide.

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

There was speculation on social media that the airline might have fallen victim to hackers, but BA insisted: "We've found no evidence that it's a cyber attack."

Air travel experts said BA is likely to be hit with massive costs in lost revenue and compensation pay-outs.

Delayed travellers are able to claim compensation under EU law, unless the disruption has been caused by factors outside the airline's control.

Malcolm Ginsberg, editor in chief at Business Travel News, said: "There is no question - the EU denied-boarding regulations will have to apply.

"They have broken all the rules and they will have to deal with it - it's going to be a very expensive situation for BA."