A flight from London City Airport was grounded on Thursday morning when an Extinction Rebellion activist boarded a plane under the guise of a passenger.
As the crew delivered their pre-flight safety demonstration, the smartly-dressed man stood up and started filming himself giving a lecture on climate change.
The protest group have taken over the capital this week in an attempt to drive home their sustainability message.
Fellow passengers can be heard urging him to make his point whilst sat down in order for the plane to take off.
But the man refuses, saying: "Sorry, I can't do that."
The air crew member repeatedly asks him to stop, which he refuses to do, prompting fellow passengers to tell him to get off the plane.
The Air Lingus flight to Dublin was meant to take off at 9.40am. It eventually left the tarmac at 11.16am.
BBC Newsnight political editor Nicholas Watt said he was one of the passengers on the plane, which was meant to be travelling from from London City Airport to Dublin.
He tweeted: "My flight from London City airport to Dublin has just been grounded by a climate change protester.
"On runway and about to take off when smartly dressed man in late middle age stood up with iPhone to deliver lecture on climate change up and down aisle.
"Cabin crew calmy and very politely asked protester to resume his seat. Politely but persistently he declined and proceeded to deliver his lecture on climate change in aisle.
"Some passengers annoyed, others listened to lecture with humour as cabin crew alerted pilot."
An Aer Lingus spokesman said: "Aer Lingus can confirm that a passenger scheduled to travel on EI283 flight from London City to Dublin airport was removed from the flight due to disruptive behaviour on board.
"The safety and security of our guests and crew is our number one priority and as a result, a full security check of the aircraft was completed prior to the flight departing.
"The flight departed at 11.16am and is scheduled to arrive in Dublin at 12.37pm. We apologise for any inconvenience caused."
Protesters plan 'Hong Kong-style' occupation of airport
Extinction Rebellion activists begun their three-day "Hong Kong-style" occupation of London City Airport on Thursday morning.
The protest group said its members intend to "peacefully occupy and shut down" the airport's terminal building from 9am on Thursday.
Activists said they will achieve this by lying, sitting or gluing themselves in front of the departure and arrival gates at the east London airport.
The latest protest is against the climate impact of flying and the Government's ongoing support of airport expansion.
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 have already signed up to take part in the protest, which will seem them "non-violently use their bodies" to close the airport.
An extraordinary number of police officers are protecting London City Airport this morning. It’s as Extinction Rebellion threaten to shut it down for up to three days, by occupying the terminal.— Rachael Venables (@rachaelvenables) October 10, 2019
Security’s stepped up - so no one can get inside now without a boarding pass. @LBCpic.twitter.com/tEyVkE37DI
A London City Airport spokesman said: "We can confirm that a number of protesters have arrived at London City Airport.
"We continue to work closely with the Metropolitan Police to ensure the safe operation of the airport, which remains fully open and operational. As of 9.15am there have been over 60 flights which have either arrived or departed.
"If you are flying from London City today, please check the status of your flight with your airline before travelling to the airport."
Hundreds of police officers are being drafted in from across England and Wales to help the Metropolitan Police with the protests, which are now in their third day.
Activists have been camped on rounds around Parliament Square and Whitehall since Monday calling for urgent action on climate change and wildlife.
The Metropolitan Police confirmed that 800 people had been arrested since Monday, with another 220 detained on Wednesday.
Metropolitan Police deputy assistant commissioner Laurence Taylor said there are plans in place to intervene and "deal proactively" with anyone who has the intention of shutting down the airport.
A London City Airport spokesman said they were working with the Met Police to prepare for the protests and all passengers would be required to show their boarding pass to access the terminal.
Two protesters have climbed onto the roof of the London City Airport entrance, and one appeared to cut his hands on the razor wire stretched around it.
They have attached a large pink banner to the wire that reads "our fragile planet is dying".
High-profile arrests: Founding member and ex-Met officer
John Curran, a retired detective sergeant of the Metropolitan Police, has been arrested at London City Airport, according to Extinction Rebellion.
The 49-year-old has been prominent at the protests all week in London.
Mr Curran, who is a father to a three-year-old daughter and now makes guitars for a living, said he is there for the future of his family.
He said on Tuesday: "Clearly there is some frustration (for the police) that they probably have better things to be doing, and I agree, but the responsibility for that must lie with the Government. Take action, and we won't have to be here."
Meanwhile, Extinction Rebellion founding member Stu Basden was also carried away by police having been arrested at the airport.
Since the start of the protests on Monday - more than 800 arrests have been made.