A Reuters journalist captured footage of environmental activist James Brown being led through the airport by police and escorted into a police van.
Last December, unexplained drone sightings disrupted flights at London's Gatwick airport, and the Heathrow Pause group aimed to pull off a similar stunt to put pressure on the government to take tougher steps to reduce carbon emissions.
But Heathrow said it remained "open and fully operational despite attempts to disrupt the airport through the illegal use of drones in protest nearby." Heathrow Pause is a splinter group of the climate group Extinction Rebellion, which blocked streets in central London this year.
It had said it would fly the drones no higher than head height and had no wish to endanger life.