Well done David Cameron in challenging Heathrow's expansion - a facility already not "fit for purpose" run for the Spanish owners of Ferrovial not the British economy. Other cities (Hong Kong, Bangkok) have taken the brave step of building new infrastructure not compounding past planning errors.

Brendon, London, UK

The airline industry has stated that the present business model is unsustainable with oil at $130/barrel.
Oil prices will not drop substantially as supply is restricted and demand grows in China etc.
There will be a massive contraction in flights, so there won't be the planes to use new runways.

David Martin, Bristol,

Only the BAA/Ferrovial will benefit from Heathrow expansion! Tens of thousands of people will have their lives blighted! The country and indeed London needs a new, high tech airport and it needs to start work today. Good Policy from Cameron!

Mel, Interlaken, Switzerland

WELL DONE DC, at last a solid view on a crazy idea in the first place. Differentiates Tories from Labour who have backed this half baked, not supported plan.

Adrian, Surrey,

We should separate the enviromental objectors to expansion
of Heathrow, Stanstead, Luton & eventually Gatwick, from people like myself who are prepared to see a 4 runway 24 hr airport in the Thames Estuary.
Whenever I see the Green Party, I see a man with a red flag walking infront of a motor car.

Peter Hooper, Windsor, UK

1. There has been no global warming for a decade.

2. NASA reported both ice caps thickening and expanding earlier this year.

3. Why is the fact that CO2 emissions have been much higher in the past and have PRECEDED warming cycles not been reported?

4. Why has the entire solar system warmed up?

S. Fermor, Redditch, Worcs.

So David Cameron is going to ration Airt Travel. If he is concerned about the environment, I suggest he starts with road user charging. No government has had the courage to really demand manage travel. Constraining UK capacity will be great news for CDG with its 4 runways.

Mike, Sussex,

I welcome DC's proposal on Heathrow ONLY if an alternate capacity is built elsewhere. The argument is spurious that building out transport infrastructure is bad for the environment. We are 20 years or less away from viable bio-fuel (algae-diesel anyone?) then our infrastructure will be badly exposed

Hany Mustapha, Kingston upon Thames, UK

Labour'sRuth Kelly, who is overseeing the Heathrow 3 debate, has failed in every government that she has worked at.

At last Mr. Cameron has come out against the third Heathrow runway, which would blight the lives of the whole of West London and in favour of improving our rail infrastructure.

Susie, London,

David Cameron knows a good thing when he sees it.
The land that Heathrow stands on is in one of the most valuable areas for industrial developement.
The time has come to build a new airport in the Thames Estuary.
It's a long term plan but so popular that Cameron may be in power for the duration.

GJB, SLOUGH (very near Heathrow), Berkshire

Bravo. The last Century replaced Smell with Noise, which is now a major enemy to the quality of life. It would be a serious crime to throw away the pleasure of living in so many parts of London. Well done David Cameron.,

Dale Cope, London,

At last a politician willing to take the threat of CO2 emissions seriously. If we allow global warming to pass from our control (the tipping point) then London and a large chunk of the UK will definitely flood, it will only be a matter of time.

John Golding BSc., London,

I welcome Cameron's opening of the debate on 'renewable' energies but why is there no mention or thought about using the potential hydro energy in the myriad of rivers in the UK? Every disused watermill has enery potential. Technology can enhance this and could, with investment, put the uk ahead.

philaustin, RAUNDS, England