London City Airport in the UK says protesters have been removed from its runway, after earlier disruption.
It says a number of flights have been delayed and cancelled after the Black Lives Matter protest.
The Metropolitan Police said it was called to the airport at 5.40am to reports of protesters "who made their way airside".
Nine demonstrators erected a tripod on the runway and locked themselves together, police added.
Seven people have been arrested on suspicion of aggravated trespass, being unlawfully airside and of breaching London City Airport bylaws.
Police said that of those who have been arrested, two have been removed from the runway.
Scotland Yard said: "Officers negotiated with the protesters and specialist officers arrived to 'unlock' the protesters. Work continues to remove the remaining protesters from the runway."
Authorities say they are "preparing the airfield to resume operations as soon as possible".
Protestors have now been removed. We are preparing the airfield to resume operations as soon as possible.
— London City Airport (@LondonCityAir) September 6, 2016
A number of flights to and from Dublin have been diverted, cancelled or "delayed indefinitely" as a result.
The cancelled services from Dublin are flights BA4461, WX114, and BA4463 - while flight BA4465 is indefinitely delayed, according to the airport's website.
While flights to Dublin affected are WX103, BA4460 and BA4462 - which are all cancelled.
It is believed that activists reached the runway after crossing docks in a rubber dinghy.
In a statement Black Lives Matter UK said that activists are carrying out the demonstration "in order to highlight the UK's environmental impact on the lives of black people".
It added that the planned expansion of London City Airport "consigns the local community in Newham to further deterioration of their environment".
The statement read: "The average salary of a London City Airport user is €136,000 (stg£113,800) and 63% of them work in business, finance or other business services. It is an airport designed for the wealthy."
"At the same time 40% of Newham's population struggle to survive on £20,000 or less."
A Black Lives Matter UK spokeswoman said: "Today we are saying all black lives matter and that includes the lives of those who live close to airports, people who are going to grow up with asthma and skin conditions.
"That also includes the lives of people living in Guinea, Eritrea and Africa who are the most vulnerable and least resilient to climate change."
