Protesters against airport expansion blocked the main access tunnel into Heathrow Airport this morning.
Three members of the activist group, Plane Stupid, blockaded the tunnel by parking a car across both lanes and locking themselves to it.
They held a banner quoting David Cameron’s election promise: ‘No Ifs, No Buts: No Third Runway’.
The access tunnel provides drivers with access to terminals 1, 2, and 3.
The group posted a picture on Twitter of traffic queuing to get into the airport.
The Metropolitan Police said officers were called at 7.42am and five arrests have been made.
The demonstration caused severe traffic delays and Heathrow warned air travellers to allow extra time to get to the airport.
It was telling drivers heading to terminals 2 and 3 to reroute to terminals 4 and 5 and take free inter-terminal transfers.
At around lunchtime the tunnel was re-opened. Heathrow thanked passengers and road users for their patience and apologised for any disruption.
The protest comes as MPs are due to debate the final report by the Airport Commission today.
Plane Stupid spokesperson Cameron Kaye said: "There is already airport capacity for families taking their yearly holiday. New runways only benefit the 15% of flyers who take 70% of our flights, cooking our planet.
"These are rich frequent leisure flyers. The most reliable predictors of frequent flyer status are a household income over £115,000 and owning a second home abroad, but it’s the poorest people who suffer most from climate change."
In July, Plane Stupid activists blocked Heathrow’s North runway, reportedly causing 22 flights to be cancelled and hundreds delayed.
