Operations ended at RAF Bentley Priory in May 2008
Plans for a World War II museum in north-west London could be jeopardised by the recession, a council has said.
Developer VSM Estates planned to sell the former RAF Bentley Priory site, in Stanmore, for conversion into apartments and a museum by 2010.
Harrow Council has said VSM is struggling to sell it due to the downturn in the property market.
VSM said the museum was central to its plans and that it would resume its attempt to sell the site in 2010.
The air base, which was the command centre during the Battle of Britain, closed in May last year and its operations were moved to nearby RAF Northolt.
The site was sold to VSM by the Ministry of Defence.
A condition of the sale was that a museum be established on the site commemorating the efforts of Spitfire pilots in World War II.
Harrow Council's portfolio holder for planning, development and enterprise, Marilyn Ashton, said: "While the site remains unsold, there is no prospect of this museum opening.
"There is therefore the real risk that this crucial piece of Second World War history will be effectively mothballed, possibly for years, until the economy stabilises."
Ms Ashton called on the government to "find a way to support a museum at a site which ensured the UK's freedom in the war against Nazism".
An MoD spokeswoman said VSM was now responsible for the site's development.
She said: "While there is no enduring operational use for RAF Bentley Priory, the MoD was clear throughout the sale of the site to VSM Estates that the heritage associated with it should be preserved in a sustainable manner."
A spokesman for VSM confirmed that it had been unable to finalise negotiations with a previous bidder.
"VSM Estates proposes to retain ownership of the site until the property market improves, and it is predicted that the site will be marketed again in 2010," he said.
The development firm was confident the museum would be built "as soon as is practicable", the spokesman added.