Passengers whose flights are cancelled or delayed as a result of environmental protests at Heathrow Airport have been warned they are unlikely to be able to get compensation.

Campaign group Extinction Rebellion has said it will target Heathrow on Friday as part of its mass protests around London.

Although passengers may be due refunds or replacement flights, they are unlikely to receive cash payouts from airlines as the protests are likely to be considered “extraordinary circumstances,” a lawyer has said.

Events such as security threats, adverse weather, unexpected flight safety issues and staff strikes are considered extraordinary.

Under the Montreal Convention, an international aviation treaty, flight operators are not required to issue compensation to passengers in extraordinary circumstances, which apply if the delay or cancellation is outside of the control and responsibility of the airline.

Coby Benson, a lawyer in flight compensation at solicitors Bott & Co, said it was likely any disruption on Friday would be extraordinary and passengers would not be due compensation.

“Based on the case law that exists at this point in time, I strongly suspect that any judge would say that this is an extraordinary circumstance,” he said.

“Mainly because it’s an event that is outside the control of the airline but also because it’s an activity which is outside the responsibility of the airline.

“It’s a given that it’s outside the control of the airline, I don’t think anyone would argue otherwise.

“But that’s just one half of it. In order for something to be extraordinary it has to be both outside the control of the air carrier and also something that is not inherent in the normal activity of the air carrier. I think it fails on both parts.”

Extinction Rebellion protests
Police officers arrive at Oxford Circus in London on Thursday (Kirsty O’Connor/PA)

The Civil Aviation Authority, the UK’s aviation regulator, said it was not yet possible to determine whether delays on Saturday would be classified as extraordinary.

While passengers may not be able to claim cash compensation, they may be due refunds or replacement flights to get them to their destination.

Under European legislation, airlines are required to refund or reroute any passengers who have their flights cancelled, even if the cause is extraordinary.

Passengers may choose between replacement flights and receiving a refund.

If the flight is delayed but not cancelled, passengers may also be entitled to “care” from the airline while they wait for it to take off.

Depending on the distance of the flight and the length of the delay, airlines could be obliged to provide food, accommodation, phone calls and transport.

Passengers are entitled to care from the airline for short flights of 1,500km or less that are delayed for two hours, for flights of between 1,500 and 3,500km that are delayed for three hours, or for flights longer than 3,500km that are delayed for four hours or more.

Extinction Rebellion protests
Campaigners at Oxford Circus in London (Kirsty O’Connor/PA)

It is unknown when the Extinction Rebellion action will begin.

The group has refused to disclose any details, although it said it had informed the police the protest would take place.

A spokesman for the group said on Thursday the disruption was “totally necessary” because of a climate “emergency”.

The Metropolitan Police said it had “strong plans” in place to deal with the protest, involving a “significant number” of officers.