Plans for a second runway at London Gatwick Airport have been approved by Transport Secretary Heidi Alexander.
Chancellor Rachel Reeves said the plans would create "thousands of jobs and billions in investment".
The £2.2bn project involves bringing the Northern Runway, currently only used in emergencies, into regular use, as well as other developments, including extending the size of terminals.
Some nearby residents have said they are "very sad" at the announcement.
The group Communities Against Gatwick Noise Emissions said it will seek a judicial review.
Read analysis from BBC Sussex political reporter Lucinda Adam
Listen: Gatwick second runway approved from BBC Radio Sussex
The Liberal Democrat MP for Horsham John Milne said he was "troubled" by the decision.
He said: "I cannot see how this expansion - alongside Heathrow and Luton - is compatible with our climate change commitments."
But he added: "This expansion doesn't necessarily mean an increase of flights over Rusper, Slinfold and Warnham. The flight path review is still undergoing."
Image source, UK Parliament
Image source, PA MediaThe Gatwick Area Conservation Campaign also said it would challenge the decision.
Chair Peter Barclay said: "This flawed decision prioritises short-term commercial interests over the long-term environmental and social costs.
"It will worsen noise pollution, traffic congestion, and carbon emissions — all in an area already under pressure."
Sally Pavey, from CAGNE, told BBC Radio Surrey: "Gatwick's Achilles' heel has always been it's lack of surface transport, the railway line can't be expanded and as it is, flyers use the residential lanes.
"This is just a cocktail of a nightmare. We can't believe the government has not held Gatwick accountable and said 'pay for the infrastructure if you want this new runway.
"There are so many holes, so many reasons to serve a judicial review.
"It's a bad day for the residents of Sussex, Surrey and Kent, and I'd say it's a bad day for the government."
Image source, PA MediaGatwick Airport’s £2.2bn second runway plan could create thousands of jobs and help “kickstart the economy”, Chancellor Rachel Reeves said.
The chancellor views the plan as a signal of the Government’s commitment to back “the builders, not the blockers”.
She said: “By slashing red tape and transforming the planning system to get Britain building again we are investing in this country’s renewal and building an economy that works for working people.”
Ms Reeves is keen to seize on any positive news for the economy as she prepares for her November budget against a backdrop of sluggish growth and inflation remaining stubbornly above target.
Image source, PA MediaSian Berry, Green MP for Brighton Pavilion, has condemned the approval.
She said: “This awful decision is a triumph for lobbying over logic.
"Despite clear reasons to reject this proposal based on noise, climate change emissions and transport gridlock, the Transport Secretary has decided to side with Gatwick bosses and plough ahead with these reckless plans.
"The excuses found to blast loopholes through conditions on resident noise and traffic gridlock set out clearly by the Planning Inspectorate earlier this year make a mockery of every hard-working resident group, environmental organisation and local council that engaged in good faith with this process."
Image source, PATransport Secretary Heidi Alexander has approved plans for a second runway at London Gatwick Airport, as the government looks for economic growth opportunities.
The £2.2bn privately-financed project involves in effect moving the current Northern Runway 12 metres to bring it into regular use, as well as other developments, including extending the size of terminals.
Chancellor Rachel Reeves said the plans would create "thousands of jobs and billions in investment", but the project has long faced opposition and the Green Party described it as "disaster".
Gatwick currently handles about 280,000 flights a year. It says the plan would enable that number to rise to around 389,000 by the late 2030s.
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