Climate campaigners’ plans to use drones to disrupt flights out of Heathrow Airport are “criminal and counterproductive”, the airport said.
Heathrow Pause, an Extinction Rebellion offshoot not endorsed by the other group, announced plans to fly toy drones within the no-fly zone, grounding all flights, on 13 September.
Organisers expect up to “a couple of hundred people” to be involved.
Heathrow airport said: “We agree with the need to act on climate change.”
The spokeswoman added: “This is a global issue that requires constructive engagement and action.
“Committing criminal offences and disrupting passengers is counterproductive.”
The activists said they “can’t stand aside” and have to act, with disruption intended to last for a number of days and potentially longer.
The group said the small, lightweight drones would not be flown above head height or on flight paths.
Flying drones over 15.5lbs (7kg) in weight above 400ft (122m) is considered “hazardous” under current legislation.
However, activists plan to operate within the three-mile (5km) no-fly zone surrounding the airport, introduced after drone sightings at Gatwick Airport in December caused about 1,000 flights to be cancelled or diverted.
The airport is to be given one hour’s notice before each drone flight, the group said, with flights planned at regular intervals, ensuring “no aircraft flights will take place”.
Extinction Rebellion said it did “not support” the actions of the new Heathrow Pause group, although both groups share many of the same coordinators.
In a statement the group said: “Extinction Rebellion UK neither condones nor condemns the action and will not be supporting it in any way.”
Scotland Yard said: “Any drone flown into the path of an aircraft has the potential to cause great harm and endanger those on board.
“Anyone caught illegally using a drone within the proximity of an airport can expect to be dealt with in line with the law.”
In a 22-page manifesto, Heathrow Pause said protestors “are prepared to be arrested peacefully”.
“Our readiness and courage are based on the conviction that our actions are a humanitarian act, this is an act of conscience, and this action is proportionate,” the group said.