The plans to build a second runway at London Stansted Airport are set to be sent to a public inquiry.
Transport Secretary Ruth Kelly is expected to formally announce the move later this week.
The move to a public inquiry means a final decision on the plans for Stansted's second runway is now not likely before 2011 at the very earliest.
The inquiry is likely to start in spring 2009, and take up to a year. It could take another year for the the government to make its decision.
Manchester was the last UK airport permitted to construct a second runway. It opened in 2001, and was the subject of a 101-day inquiry during the mid-1990s.
The Stansted Airport expansion plans were announced by the airport's operator BAA in March.
The plans comprise the new 3,000-metre runway, as well as a second terminal building, new taxiways and aprons, new air traffic control tower and associated infrastructure improvements.
The total planned cost of the project is £2.3 billion.
Campaign group Stop Stansted Expansion (SSE) commented: "The final decision on this project will be taken not by this government but by the next one, and the Conservatives have long realised there is no economic case for doubling the size of Stansted".
They added: "It also makes no sense as an investment for the owner of the airport, particularly when the owner is strapped for cash, as BAA is".
Meanwhile, the government is due to make a decision on passenger numbers at Stansted.
The airport is currently restricted to handling 25 million passengers per year (in 2007 it handled 23.5 million), but BAA has pushed for this ceiling to be raised to 35 million.
Last year, local authority Uttlesford District Council rejected this plan - which in turn went to a public inquiry.
Transport Secretary Kelly is due to announce the government's decision on the passenger numbers later this week, in tandem with the formal announcement of the second runway public inquiry.
Source - Airport International's Aviation Correspondent
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