Environmental campaigners are planning to fly drones around Heathrow in an attempt to ground flights.

Activists with Heathrow Pause, a splinter group of Extinction Rebellion, have said they will operate small toy drones from 3am on Friday 13 September.

A spokesman for the organisation said it expected “somewhere between 50 to a couple of hundred people” to be involved in the action, with each person using a drone. With disruption intended to last for a number of days and potentially longer, the activists said they “can’t stand aside” and had to act.

“From 13 September, we will exploit a loophole in Heathrow airport’s health and safety protocols and fly toy drones within its restricted zone,” the group said. “It is our understanding that the airport’s authorities will respond by grounding all flights. Drones will not be flown in flight paths and there will be no risk of harm to anyone.

“We know that we will be arrested. We know that we face significant prison sentences for our actions. We have lives, we have families, we do not wish to go to prison. But we are steadfast in our resolve. We do this in defence of life. We do it because our consciences leave us no other choice but to act.”

The group said the small, lightweight drones would not be flown above head height or on flight paths, and activists planned to fly them within the three-mile (5km) exclusion zone surrounding the airport.

With the airport to be given an hour’s notice before each flight, drones will be flown at regular intervals, ensuring that to “comply with Heathrow’s own rules, no aircraft flights will take place”.

A Metropolitan police spokeswoman said the force was aware of the planned protest.

“Any drone flown into the path of an aircraft has the potential to cause great harm and endanger those on board,” she said. “Anyone caught illegally using a drone within the proximity of an airport can expect to be dealt with in line with the law.”

The activists said they would meet police and airport authorities on Friday to discuss their plans.