Climate activists plan to take their campaign to London’s Heathrow airport on Friday after disrupting public transport and snarling roads and bridges in the U.K.’s capital for the past four days.

Demonstrators are planning “action” Friday at Europe’s busiest airport as part of a two-week protest against the effects of climate change, according to a spokeswoman for the group called Extinction Rebellion. She declined to give further details about the plan, which will coincide with the start of a four-day Easter weekend in the U.K. that’s generally a busy travel period.

“We are working with the authorities to address any threat of protests which could disrupt the airport,” a spokeswoman for Heathrow said by email. “While we respect the right to peaceful protest and agree with the need to act on climate change, we don’t agree that passengers should have their well-earned Easter Break holiday plans with family and friends disrupted.”

Earlier on Thursday, dozens of demonstrators halted traffic on Vauxhall Bridge, according to a Twitter post from Transport for London, while Waterloo Bridge, the city’s busiest river crossing, has been closed since Monday after people chained and glued themselves beneath a truck.

Vauxhall Bridge links the south bank of the Thames near the headquarters of Britain’s MI6 Secret Intelligence Service and the new U.S. Embassy with the Pimlico district close to the Tate Britain art gallery and a number of government buildings.

Extinction Rebellion activists have also blocked Parliament Square and junctions at Marble Arch and Oxford Circus, and say the protest will go on through next week at least. Police have made more than 400 arrests, including three people who pleaded not guilty to obstruction after attaching themselves to a Docklands Light Railway train in the Canary Wharf financial district.

The demonstrators are demanding that the U.K. acknowledge the “crisis” posed by global warming, enact legally binding policies to reduce net carbon emissions to zero by 2025, and form a citizens assembly to oversee changes.