It's costing tens of millions of pounds and will take another year to be completed.
A major project to refurbish and strengthen the famous road tunnels leading to Heathrow airport is continuing.
It's to improve safety and allow for the new generation of heavier planes using the runway above.
The work is being carried out during the night so the airport can operate as normal during the day.
Our transport correspondent Mike Pearse has more.
A six-week public consultation on plans for a second runway at Gatwick is due to start today. Airport bosses say it would be the biggest ever boost to the local economy - worth £56bn and creating 19,000 new jobs.
Campaigners say it'll double aeroplane noise and affect the environment.
Gatwick Airport has today revealed plans for a controversial second runway.
It would cost £7 billion pounds and open in 2025. The airport says it would be the biggest-ever boost to the local economy- £56 billion pounds and with 19,000 new jobs.
Gatwick say a third runway should not be built at Heathrow and are launching a massive campaign against it.
Our Transport Correspondent Mike Pearse reports.
The owners of Gatwick Airport have released footage of their plans to build a new runway.
The airport claims that the expansion would help the UK connect to 27 more destinations than a third runway at Heathrow, while a key architect behind the plans suggests the move could spark an Olympic-style boost for the economy of south London.
- Gatwick claims a second runway, to open in 2025, would link the UK to more destinations than a three-runway Heathrow
- Heathrow and Gatwick were shortlisted as favourites in December by the government's Airports Commission
- Commission chairman Sir Howard Davies said a new airport in the Thames estuary merited further investigation but a so-called "Boris Island" is now thought increasingly unlikely
The owners of Gatwick Airport vowed today to start building a controversial second runway by 2020. The announcement is the latest salvo in the battle between Heathrow and Gatwick to win government backing for airport expansion.
Around 4,000 households most affected by noise from a possible second runway at
Gatwick will get £1,000 towards their council tax, bosses of the West Sussexairport have promised.
The pledge involves annual compensation and is equivalent to Band A council tax. Gatwick chiefs are pressing hard for an extra runway and such an option is on the shortlist now being considered by the Whitehall-appointed Airports Commission.
Expansion at Gatwick would, without doubt, deliver many upsides for our local community in terms of jobs and investment. But we must also recognise the negative noise impacts on local people from more flights. Gatwick's location obviously means that comparatively fewer people would be affected by a new runway. However, I believe we must do more to help those that would be affected. Under the scheme, we are pledging £1,000 towards council tax for qualifying households in the local area, if and when a second runway became operational."
One of those opposed to a second runway at Gatwick is Horsham Tory MP FrancisMaude. He addressed more than 300 residents of the village of Warnham who areobjecting to a new Gatwick flight path trial.
Even these last few weeks, with the weather keeping people indoors and off-season traffic levels, the noise from the flight path trial has been unacceptable for local residents. When high holiday season is on us, with the warm weather enticing people outside, the effects are likely to be intolerable. So I'm urging (air traffic control company) Nats and Gatwick to call time on this trial now. We've had the trial. It's failed."
Executive Manager of Lydd Airport, Hani Mutlaq, talks to ITV reporter Tom Savvides about the airport's expansion plan that has now been approved by the Government.
The owners of Gatwick Airport say they are preparing to launch a bid to build an additional runway.
They say by increasing the capacity at the Sussex site the government can avoid controversial proposals to expand Heathrow.
But the news is unlikely to be welcomed by those living nearby. Our correspondent Andrew Pate speaks to David Rowlands, Chairman of Gatwick Airport.
In February this year, our political correspondent Phil Hornby had a look at the options for airport expansion in the south and south east. It was before the London Mayoral election, and candidate Ken Livingstone proposed expansion at Stansted or... Gatwick.
In this report, Phil spoke to the then Transport Secretary Justine Greening, David Cameron, Ken Livingstone and Colin Matthews, chief executive of the British Airports Authority.