Extinction Rebellion activists are threatening to shut down Heathrow Airport with drones.
The climate change protest group vowed to stage a one-day demonstration in June and then 10 further days in July – unless the government cancels plans for expanding the airport.
Ten days of protests across central London in April saw 1,130 people arrested for various offences.
Heathrow Airport said the plan was “reckless” and could “endanger lives”.
Extinction Rebellion said it was in talks with members about carrying out action to close the airport on 18 June and again from 1 July for up to 10 days if the government did not cancel plans to expand the airport.
A spokesman for the group said it was “fully committed to non-violence” and it would “not take action that would put airline passengers at risk” but “in the face of climate and ecological collapse [would] continue to build a peaceful movement”.