Protesters at Terminal 5 chanted "no third runway"
Hundreds of activists opposed to a third runway at Heathrow have staged a protest at Terminal 5.
Up to 300 protesters wearing red T-shirts with the words "stop airport expansion" took part in the hour-long protest, chanting "no third runway".
Organisers include environmental and residents' groups, such as those from the village of Sipson, which will be flattened to make way for the runway.
It is the first major protest since the government's go-ahead for expansion.
Transport Secretary Geoff Hoon announced the government's decision on Thursday.
He said the business case for more capacity at the airport was compelling.
Business leaders warned that Britain's competitive advantage in Europe would be compromised if capacity at the airport did not increase.
But on Saturday campaigners said they would fight the decision, vowing to win the "political war".
In a show of solidarity for the village of Sipson, campaigners taking part in the protest said they were ready to move into homes facing destruction.
'Hoon' in stocks
Leila Dean, 29, of campaign group Plane Stupid, said: "We came here because we are supporting the 700 villagers who will lose their homes if the plans go ahead.
Campaigners said they will fight the government's decision
"We are ready to move into their houses if the runway goes ahead, but we don't think it's going to come to that because no one wants the runway."
Other demonstrators pelted a man dressed as Geoff Hoon with sponges as he stood in make-shift stocks.
Another campaigner dressed as the Prime Minister Gordon Brown, complete with mask.
Marina Pepper, 41, of Climate Rush, said: "Now the decision has been made, it is heart-warming to see the broad base of opposition."
Up to 700 homes will be demolished to make way for the runway, to allow Heathrow's flight capacity to rise from 480,000 to 702,000 per year.
Environmental campaigners have also said the decision leaves the government's legal commitment to cut carbon emissions by 80% by 2050 in tatters.
But Mr Hoon said strict measures would be put in place to limit noise and emissions.
Responding to threats to close down Heathrow, a BAA spokesman said: "We respect people's right to protest but we would ask people to respect passengers' rights to fly."
A Society of British Aerospace Companies spokesman said: "If we grounded every flight in the UK we would lose that and more but would only cut global CO2 emissions by 0.1 per cent.
"When you look at the facts around flight the only rational decision is to expand Heathrow and we congratulate the government on taking the right, but tough, decision for the national interest in the face of opposition from small but vocal minority groups."
Work on a new runway is not likely to start until 2015 and the runway is not expected to be operational for at least a decade.