A group of nine protesters have shutdown the runway at London City Airport by locking themselves together.
The Black Lives Matter group says it’s highlighting the effect climate change has on “black people locally and globally”.
Scotland Yard’s investigating reports people managed to get air-side by swimming across a dock.
The airport said inbound flights were being diverted and it hoped to “resume operations as soon as possible”.
The runway has been closed, with all outbound flights being cancelled and all incoming flights being diverted to Gatwick and Southend.
The Met Police said it was called to the site at about 05:40 BST and officers remain in place trying to defuse the situation.
A record 4.3 million passengers used the airport last year.