The Government is expected to give the go-ahead to controversial airport-expansion plans that are likely to start with a third runway at Heathrow.
Consultation on proposals for new construction at Heathrow, Gatwick and Stansted airports, opposed by local residents and environmental groups, closed several weeks ago.
No formal decision has been taken, but Alistair Darling, the Secretary of State for Transport, is understood to have been persuaded of the economic case for a new runway at Heathrow, as well as leaving the option open for a second runway at Stansted and even the construction of a new terminal there. Gatwick's freeze on expansion, valid until 2019, is unlikely to be overturned at this stage.
Mr Darling, backed by the Treasury, will make a formal announcement on airport expansion later this year.
Officials in his department have warned the minister that any decision in favour of new runways will provoke a public outcry. But a recent Mori poll for Freedom to Fly, an aviation industry umbrella organisation, showed public support for expansion had fallen only four points - from 80 to 76 per cent.
Anti-airport campaigners are braced for an announcement favouring Heathrow. "That is the hot favourite," said one campaigner. He said BAA, which owns Heathrow, was already pushing hard to win local support from local councils that are hostile to the plan.
To pre-empt opposition from environmentalists, Mr Darling is understood, in conjunction with Gordon Brown, the Chancellor, to be drawing up a list of options for "green" taxation, including changes to duty on aviation fuel, which is currently not taxed.
It is estimated that a third, short runway at Heathrow, designed for medium-sized aircraft, would increase flight numbers by nearly half by 2030, with the accompanying benefit of £8bn in revenue.
The Heathrow scheme has support from the aviation industry and trade unions. British Airways is thought to have been a strong advocate.
Jeff Gazzard, a campaigner with the Aviation Environment Federation, said BAA and the Government had to overcome problems with air pollution and the presence of the A4 trunk road between the site of the proposed runway and Heathrow's terminals. "Any half-decent planning inquiry inspector would turn this down," he said.
Whitehall sources indicated the Government had given industry representatives the clear impression the runway schemes would be approved.
The Department of Transport insisted that no decisions had yet been taken on airport expansion. "It is too early to say," said a spokesman.