London City Airport was brought to a standstill on Tuesday for more than five hours after nine protesters from the Black Lives Matter campaign gained access to the runway.
Flights were disrupted since 5.40 am local time when the protesters lay down in the middle of the tarmac.
The Metropolitan Police said the protesters had erected a tripod on the runway and locked themselves together.
All nine protesters have been arrested on suspicion of aggravated trespass, being unlawfully airside and breaching London City Airport bylaws, and taken to east London police stations.
The activists reportedly managed to get across the Royal Docks to stage a demonstration on the runway. There are suggestions they used a rubber dinghy, raising concerns about airport security.
The movement says the aim of the demonstration is to “protest the UK's environmental impact on black people.”
“Airports, power plants, and the busiest of roads in the West tend to be in the most disadvantaged working class areas, where a disproportionate number of black and brown communities live," Black Lives Matter UK said in a video posted on Facebook.
“Environmental racism means that black people in Britain are 28% more likely to be exposed to air pollution than their white counterparts," the video continues, adding that "climate crisis is a racist crisis."
Previous reports stated that Plane Stupid, a group dedicated to taking direct non-violent action against aviation expansion, was behind the stunt.
The group has expressed "solidarity" with the Black Lives Matter movement on its official Facebook page.
According to the protest group, the demonstration is focusing on the airport's expansion plans, which they claim will favour the "wealthy" passengers and ignore the local population of Newham.
It said: "Recently London City Airport was given approval to expand its capacity, a move that consigns the local community in Newham to further deterioration of their environment.
"The average salary of a London City Airport user is Euro 136,000 and 63 percent of them work in business, finance or other business services. It is an airport designed for the wealthy.
"AT the same time 40 percent of Newham's population struggle to survive on £20k or less."
Flights to Zurich, Geneva, and Guernsey had been cancelled, while flights due to arrive from Rotterdam, Luxembourg, New York, and Frankfurt were diverted.
The Metropolitan Police are investigating how the protestors managed to get airside.
Some have expressed anger at authorities for taking too long to put an end to the situation.
A £344 million ($458.4 million) expansion project for the airport was given the green light in July.