Local residents oppose a third runway at Heathrow

The airlines and the TUC are launching a �100,000 advertising campaign.

In an open letter to newspapers, they will argue that the Heathrow runway would create benefits worth �37bn to the UK and 24,000 direct jobs by 2030.

Transport Secretary Alistair Darling is due to announce soon whether he backs expansion at Heathrow or Stansted.

Stansted...will never be able to compete with Paris Charles de Gaulle, Frankfurt International or Amsterdam Schiphol airports Open letter from Heathrow's supporters

Heathrow's supporters estimate that the new runway would create a further 80,000 jobs indirectly.

If the government decides to build at Stansted rather than Heathrow, the UK will lose aviation business to Paris, Frankfurt and Amsterdam, their letter warns.

"While Stansted should be developed in the future, it will never be able to compete with Paris Charles de Gaulle, Frankfurt International or Amsterdam Schiphol airports."

"If the right decision is not taken now, our aviation industry will be diminished, impacting not only London, but also the British economy."

'Environmental challenges'

The letter is signed by BA's chief executive, Rod Eddington, Virgin Atlantic chairman Sir Richard Branson, bmi's chairman, Sir Michael Bishop, and Brendan Barber, general secretary of the TUC.

They say they are confident "environmental challenges can be resolved".

The airlines have previously said they are not ruling out taking legal action against the government if it backs the expansion of Stansted over Heathrow.

They are concerned that the development would be cross-subsidised through higher landing charges being levied at Heathrow.

'Enough is enough'

Last week, Prime Minister Tony Blair was handed a 4,000-name petition calling for the expansion at Heathrow to be ruled out.

Campaigners say the move would add to the noise and pollution already suffered by residents in west London.

London Labour MP Ann Keen said a third Heathrow runway would be "a step too far".