Gatwick's second runway has been given the go-ahead by the government.
The northern runway already exists parallel to Gatwick's main one, but cannot be used at the same time, as it is too close.
It is currently limited to being a taxiway and is only used for take-offs and landings if the main one has to shut.
The £2.2bn expansion project will see it move 12 metres further away to solve the problem, facilitating 100,000 extra flights a year and 14,000 jobs.
The airport is already the second busiest in the UK, and the busiest single runway airport in Europe.
No public money is being used for the expansion plan, which airport bosses say could see the new flights take off from the second runway by 2029.
It was initially rejected by the Planning Inspectorate over concerns about inadequate provisions for noise prevention and public transport connections.
Campaigners have argued the additional air traffic will be catastrophic for the environment and the local community.
A revised plan was published by the planning authority earlier this year, which it said could be approved by the government if all conditions were met, giving a final deadline of 27 October.
A government source told Sky News on Sunday: "The transport secretary has cleared Gatwick expansion for take-off.
"It is possible that planes could be taking off from a new full runway at Gatwick before the next general election.
"Any airport expansion must be delivered in line with our legally binding climate change commitments and meet strict environmental requirements."
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