Organizer Joshua Virasami said that the movement - founded to protest the killings of black people by American police - was needed "in Britain and all over the world."
London's Metropolitan Police says officers made several arrests among those blocking a road leading from a main highway to Heathrow on Friday morning.
Police say one lane is open but traffic is backed up getting into one of the world's busiest airports, AP reported.
Heathrow says it's not aware of passengers missing flights because of the protest.
Demonstrators in the city of Nottingham also lay down on tram tracks in the city.
