A climate protester glued himself to a plane and another held up a flight with a speech on global warming Thursday as campaigners tried to "occupy" a London airport near the capital's global financial hub.
London police reported making more than 1,000 arrests over four days of protests by the group Extinction Rebellion, which have been staging a global effort stretching from Sydney to New York.
Their biggest British action to date saw hundreds try to lay siege of London City Airport in protest at its management's expansion project.
AFP reporters saw uniformed officers carry or escort around 100 demonstrators from outside its main entrance.
One man in a brown business suit climbed over coils of barbed wire and onto the roof of the east London airport's entrance before coming back down and being led away by the police.
Dozens more staged a sit-in at the nearby train station during the morning commute.
"I decided to come and join them because I think they have a just cause," pensioner Steve Phillips told AFP as around 100 campaigners rallied in the presence of dozens of police.
"People are flying in and out, and the cost for the planet is unimaginable."
A morning flight to Dublin was delayed by nearly two hours after a passenger got up to make a speech about the climate as the plane prepared to take off, airport and Aer Lingus airline officials said.
A London City Airport spokesman said the captain exercised his right to arrest the passenger under international flight safety rules.
Metropolitan Police deputy assistant commissioner Laurence Taylor said "some interesting attempts" had been made to disrupt flights.
"One man had glued himself to the top of an aircraft," Taylor said in a video message.
"He has of course now been removed and our policing operation continues there."
UK media identified that person as 2012 London Paralympic Games cycling bronze medallist James Brown.
"I don't know how the hell I got up here," the partially-blind Brown said in a selfie shot atop a British Airways plane that went viral on social media.
"I don't know how the hell I'm gonna get down again," he said before turning off his camera.
Extinction Rebellion is spearheading a two-week global action that kicked off Monday with partial shutdowns of traffic in cities around the world.
Group members also blocked a street outside the Louvre Museum in Paris and a bridge overlooking the Reichstag parliament building in Berlin.
- Police more assertive -
Extinction Rebellion's colourful protests have managed to attract a mass following since its creation last year by UK academics studying the effects of harmful carbon emissions on Earth.
The group's growing list of prominent supporters include actress Emma Thompson and the Swedish teen climate activist Greta Thunberg.
Extinction Rebellion's last big event in London in April managed to shut down central parts of the city for 11 days and led to more than 1,000 arrests.
Police are now being more assertive.
London's Metropolitan Police on Thursday enacted a rarely-used measure in the 1986 Public Order Act aimed at preventing "serious disruption to the life of the community".
"Any assembly linked to the Extinction Rebellion 'Autumn Uprising' and those linked to it who wish to continue their assembly MUST go Trafalgar Square and only assemble in the pedestrian area," it said.
Deputy assistant commissioner Taylor said the protests had now been mostly contained to the picturesque central London square.
Extinction Rebellion had vowed to continue targeting the airport until Saturday evening -- and to wind down their global action only at the end of next week.
The group wants governments to adopt policies that cut harmful emissions to a net level of zero by 2025.
Britain has set itself the target of 2050.