The peaceful blockade began on Thursday and is expected to last around three days.
Activists are hoping to emulate Hong Kong-style demonstrations, sitting in front of doors to block passengers from passing through the airport.
James Brown, a Paralympic bronze medallist, went one step further, climbing on to the hull of a British Airways plane.
Another activist caused a flight to be grounded after standing up and speaking about the climate crisis when the plane was due to take off. The plane was made to return to the terminal.
A number of media outlets have reported several arrests made following the protest.
Airport staff are working in tandem with the police to guarantee passengers’ safety. People are being encouraged not to change their travel plans, but to inform themselves about current flight information. Some flights are experiencing delays, but the majority are only delayed by around ten minutes.
