A plane has returned to the terminal of London City Airport after a climate change protester disrupted the flight, according to Sky sources.
Pictures show the protester being arrested by police before he was led off the plane.
The arrest comes as hundreds of demonstrators attempt to shut down the transport hub in protest against the climate impact of air travel.
Extinction Rebellion activists are beginning what they call a three-day "Hong Kong-style occupation of the terminal building".
Several other arrests have been made at the airport, where some protesters have glued themselves to the floor.
Footage shared by a Twitter user shows a demonstrator on a plane on the runway.
The protester can be heard telling an air hostess: "I don't wish to travel with you but I don't wish to get off."
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He adds: "I'm extremely sorry for the inconvenience."
A passenger off-camera is then heard saying to the air hostess: "Can you do us all a favour and remove him from the plane?"
The protester then continues: "We have two generations of human civilisation left if we carry on doing what we're doing."
Extinction Rebellion said earlier that it intended to "peacefully occupy and shut down" the airport's terminal building from 9am.
The Metropolitan Police is yet to give an exact figure for how many protesters have been arrested.
Sky's home affairs correspondent Mark White is at the airport, where a protester was seen on a low roof in the terminal building.
Footage shows people below cheering as the demonstrator shouts something from the rooftop.
Sky's senior correspondent Ian Woods, who is also at the site, said there were "early arrests" as protesters attempted to shut the airport down.
Officers have also been seen escorting demonstrators out of the airport's Docklands Light Railway (DLR) station.
Protesters said earlier they want to stop flights by lying, sitting or gluing themselves in front of departure and arrival gates.
They added that they planned to occupy the airport's access road and the DLR station if they could not make it into the building.
Extinction Rebellion spokesperson Rupert Read said: "By non-violently shutting down this airport, in homage to the style of the Hong Kong democracy protesters, we are demonstrating the utter frailty of the transport systems that countries such as ours, unwisely, have come to depend upon."
The group said hundreds of people had signed up to take part in the protest.
It said those taking part are willing to risk being arrested to achieve their aim.