Protesters warned of civil disturbances if their opposition was ignored
Thousands of campaigners opposed to plans for a third runway at Heathrow joined a protest rally outside the west London airport.
An estimated 3,000 protesters marched from Hatton Cross to Sipson, the village that would be lost if the planned runway goes ahead.
They then gathered to form a giant "NO", that could be seen from the air.
Campaigners say the planned expansion would have a serious impact on hundreds of thousands of homes in the area.
But business groups and airlines claim the third runway is essential.
MPs, local council leaders and environmentalists addressed the crowds.
Speakers included London's deputy mayor Richard Barnes.
He said: "I've represented Hillingdon for 20 years and this is not the first time I've fought Heathrow airport expansion.
"They keep lying to us but this time we will win because we have cross-party support."
Economic expansion and growth is all very well for those making the money but the damage it's doing to the planet is not acceptable
Lewis Jones, protester
In November last year the government set out proposals for a major expansion at Heathrow, which could see the building of a third runway and a sixth terminal.
The new runway would be 2,200m (about 7,200ft) long and could be in operation by 2020 if it got the go-ahead.
The government has said it would meet noise and air quality targets, but the entire village of Sipson with about 700 homes would be destroyed.
Protester Anna Serdaris, 50, from Athens, said: "We have the same problem at Athens airport and I felt I needed to show my support.
"It's ironic that I've had to fly here this morning to protest against airport expansion but people need to listen."
Campaigners say expansion will affect hundreds of thousands of homes
Lewis Jones, 21, from Roehampton said: "I'm here just because the public need to know.
"Economic expansion and growth is all very well for those making the money but the damage it's doing to the planet is not acceptable. This is building momentum."
The Archbishop of Canterbury also backed protesters and a letter from Dr Rowan Williams was read out at the rally.
It said: "Concern for our environment is a clear imperative arising from the respect we owe to creation and to each other.
"So questions of airport expansion, like all developments at risk, increasing the damage we do to our global environment (which still impacts hardest on the poorest) cannot be considered uncritically, or in a morality-free zone."
But Lord Soley, campaign director of pro-expansion group Future Heathrow, said opinion polls showed local people were in favour of expansion.
"Local people know that the airport is vital to the local economy and supports jobs and business," he said.
"A third runway will only go ahead within environmental limits on noise and air quality."
Event organiser Tamsin Omond heralded the demonstration a success.
She said: "We've had 3,000 people make the effort to come out here and tell the government we don't want a third runway. And it's not just the usual suspects." But Ms Omond warned the government there was serious intent behind the protest.
"The people have become politically active and if the government doesn't reverse its policy, people will become politically frustrated. The third runway will not be built - I'm talking civil disturbance."
The public consultation period over the proposals ended on 27 February, and final policy decisions are expected to be taken some time next year.
The protesters gathered in a field to form their protest message
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