Transport Secretary Alistair Darling today announced a new runway could be built at Gatwick.
But he did opt to honour a legal agreement between airport operator BAA and residents which bans development until 2019.
In a Commons statement, he said no building work should take place before this date.
Mr Darling also said land must be put aside to build the second runway but the project's future will depend on plans for a third runway at Heathrow.
If Heathrow cannot meet "stringent environmental limits" Gatwick will be developed.
Experts have already cast doubt on whether limits on pollutants can be achieved at the London airport.
Gatwick has a "strong case" for development on its own merit, Mr Darling said.
Hove MP Ivor Caplin, who campaigned for a second runway to safeguard thousands of jobs and boost the Sussex economy, welcomed the announcement.
He told The Argus: "This is a hugely important and significant decision by the Government which safeguards the future of Gatwick.
"It is vital to jobs and offers the best environmental solution for the South-East of England, to deliver greater passenger numbers and economic benefits to our county - on the coast in Brighton and Hove but also Sussex as a whole."
The most dramatic option for two new runways was ruled out.
But the new runway would still lead to the destruction of at least 200 homes and acres of green belt land.
Some roads will have to be closed and the M23 will have to be widened, along with the A23 access road.
A Government source said Mr Darling had listened to both sides of the argument at Gatwick.
He added "The Secretary of State is looking at air travel over the next 30 years, not just the next 15."
Elsewhere, Mr Darling said the Government had concluded that a new runway should be developed at Stansted Airport, to be opened around 2011 or 2012.
He said ministers had concluded that it would not support the development of a new airport at Cliffe, Kent.
And he told MPs that land would be safeguarded at Edinburgh for a possible second runway and the Government was recommending that consideration be given to protecting land at Glasgow for a possible new strip.
The Transport Secretary said the Government supported the development of additional terminal capacity at Manchester, provided noise impact can be controlled.
And he agreed that Liverpool airport should be expanded and the runway lengthened.
It also supported terminal and runway extensions at Newcastle, Teesside and Leeds-Bradford.
Mr Darling said the Government was not supporting the development of a new airport between Coventry and Rugby, but did support a second runway at Birmingham, subject to stringent limits on noise and to be built around 2016.
He added that the Government supported expansion of passenger and freight traffic at East Midlands Airport, but saw no immediate need for a second runway there.
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