Protesters lay on the road near Heathrow airport on Saturday in a demonstration that led to more than a dozen arrests.
The climate change activists rushed on to the M4 Spur Road where they lay down and refused to move in a demonstration against the £16 billion planned third runway at the airport which was announced last month.
Traffic was brought to an almost standstill as cars were forced to stop, but by mid-afternoon traffic was said to have returned to normal.
The Met arrested 15 people for obstructing the highway and public order offences at the protest which was organised by campaign group RisingUp.
Campaigners held signs which read “protect the planet, no more runways” and “residents against aircraft noise” and chanted: “No ifs, no buts, no third runway”.
A spokesman for the group said: “The Government’s decisions to expand Heathrow, despite mass opposition from local residents and the fact that doing so is incompatible with the UK’s own laws on climate change, leaves us with no morally acceptable option but to resist.
“Only 15% of the British public is responsible for 70% of international flights taken in the UK and Heathrow largely serves international passengers who have a mean income of £57,000 per year.
“This expansion is being driven by the very rich at the expense of some of the poorest people in the world.
Neil Keveren, a resident of nearby Harmondsworth, said: “Democracy has failed us. Elected leaders have totally reversed the will of the people.
“As a direct result, the quality of life and life expectancy of the population here will be shorter. This is against our human rights and must be defended.
”Who is left to correct this injustice when our politicians will not? The answer is us - you and me.”
Ex-MP Zac Goldsmith, who resigned from his Richmond Park seat last month over the airport decision, was seen speaking to campaigners at the demonstration.
Liberal Democrat candidate for Richmond Park Sarah Olney, former climate change secretary Ed Davey and Ukip’s Suzanne Evans also attended the protest.
Before the event the Met said it had a “proportionate policing plan in place and if there is criminal behaviour that leads to serious disruption or danger to anyone we will have a robust response to minimise disruption and maximise public safety”.
A spokeswoman for Heathrow told the Evening Standard: “We can confirm that a number of climate change protests are taking place at Heathrow today. Whilst we respect the right to peaceful protest, the safety of our passengers, aircraft and colleagues, together with the smooth running of the airport, is paramount.
“We are working with the police to minimise any disruption, however passengers should allow extra time to travel to the airport, or use public transport where possible.”