A fierce debate about airport capacity is raging after a long-awaited report recommended that a new runway should be built at Heathrow rather than Gatwick.
After three years of investigation, the Airports Commission said Heathrow was best placed to provide "urgently required" capacity, but the move was met with strong resistance from local people - and landed the Prime Minister with a huge headache.
David Cameron will have to decide, probably later this year, whether to accept the recommendation, risking a rebellion from figures including London Mayor Boris Johnson.
He will also be performing a humiliating U-turn on his own "no ifs, no buts" promise made years ago that Heathrow expansion would not go ahead.
Mr Johnson, seen as a potential successor to Mr Cameron, made clear his continued opposition to an expanded Heathrow, predicting that a third runway "will never be built".
But business leaders and unions welcomed the commission's report, saying it will pave the way for tens of thousands of new jobs and give a huge boost to the economy.
The commission opted for a new, full-length runway at Heathrow rather than expanding one of the airport's current runways or building a new one at Gatwick.
It also recommended a "comprehensive" package of measures to make Heathrow 's expansion more acceptable to the local community. This includes a ban on night flights from 11.30pm to 6am, legally binding limits on noise, a new levy to fund insulation for homes, schools and other community facilities around Heathrow, and an independent noise authority.
Environmentalists warned that building a new runway at Heathrow will make it harder to solve the problems of air pollution and climate change emissions which the UK already faces.
The Government has been ordered by the Supreme Court to urgently produce a plan to improve poor air quality in the UK, which causes thousands of premature deaths and disease a year, to meet European Union legal limits.
Commission chairman Sir Howard Davies warned that London's airports were showing signs of "strain" and the entire system would be full by 2040 without action.
No new full-length runway has been built in south-east England since the 1940s, while other countries have kept pace with the growing demands of an expanding aviation industry, said the commission. Its 242-page report also recommended that a fourth runway at Heathrow should be "firmly ruled out".
The cost of building a new runway is estimated to be around £17.6 billion, said the commission, with billions more in transport costs.
The commission said a new runway would generate up to £147 billion in economic output over 60 years and create more than 70,000 jobs by 2050.
Regular daily services to around 40 new destinations would be added, including 10-12 new long-haul flights.
Gatwick had presented a "plausible" case for expansion and was well placed to cater for growth in European leisure flying, but was unlikely to provide capacity which was urgently required - long-haul destinations on new markets, said the report.
"Heathrow can provide that capacity most easily and quickly. The benefits are significantly greater, for business passengers, freight operators and the broader economy," said Sir Howard.
The commission had ruled out a new airport in the Thames Estuary, favoured by Mr Johnson, as "infeasibly expensive and hugely disruptive for many businesses and communities".
A new runway at Heathrow would provide the necessary capacity until 2040 at least, said Sir Howard.
"Beyond that the position is uncertain and will be strongly dependent on the international policy approach to climate change."
A ban on night flights would affect 16 which currently land at Heathrow between 4.30am and 6am. This would only be possible with expansion, said the commission.
A "noise envelope" would be agreed, legally binding Heathrow to stay within limits. This could include stipulating no overall increase above current levels.
The commission also recommended that Heathrow should compensate residents who would lose their homes - estimated at 783 - at full market value plus 25% and reasonable costs.
The airport should also be held to its commitment to spend more than £1 billion on community compensation, the report said. It also called for an aviation noise authority to be set up, with a statutory right to be consulted on flight paths.
New investments in railways should be made and a congestion charge for cars arriving at Heathrow should be considered, it was urged.
John Holland-Kaye, chief executive of Heathrow Airport said: "This debate has never been about a runway, it's been about the future we want for Britain.
"Expanding Heathrow will keep Britain as one of the world’s great trading nations, right at the heart of the global economy.
"Our new plans have been designed around the needs of local communities and will meet carbon, air quality and noise targets, and provides the greatest benefit to the UK’s connectivity and its long-term economic growth.
"We will create the world's best connected, most efficient and most environmentally responsible hub airport at the heart of an integrated transport system. The commission has backed a positive and ambitious vision for Britain. We will now work with Government to deliver it."
But Gatwick Airport's chief executive Stewart Wingate said: "Gatwick is still very much in the race. The commission's report makes clear that expansion at Gatwick is deliverable.
"It is for the commission to make a recommendation but it is of course for the Government to decide.
"So we now enter the most important stage of the process. We are confident that when the Government makes that decision they will choose Gatwick as the only deliverable option."
He would not rule out a legal challenge, although Sir Howard made it clear the commission had taken legal advice throughout its deliberations.
Responding to Mr Wingate's comments, he said: "He is not in our race. There are economic benefits to expanding Gatwick but they would be smaller."
If the Government makes an early decision, a third runway could be open by 2026, he said.
Sir Howard said it was possible that passengers driving to Heathrow could pay a congestion charge of £20 in a bid to make more people travel by public transport.
He also raised the possibility of a 50p levy on passengers to raise money to compensate local people.
Sir Howard said fares in London could increase by £20 by 2050 if the new runway is not built.
Sir Howard is now planning a holiday in the Azores, flying from Heathrow.
Asked about comments by Mr Johnson that the new runway would never be built, he replied: "He says a lot of things. We had the benefit of talking to real people, as well as the mayor.
"There are a lot of shaded views among people around the airport, but many are anxious about it closing."
John Longworth, director general of the British Chambers of Commerce, said: "After three years of deliberation, businesses across the UK will be pleased that the Airports Commission has finally come to a clear recommendation.
"Now that all the evidence is on the table, firms in every corner of the UK want to see an irreversible Government commitment to a new runway at Heathrow by the end of 2015, with planning complete and diggers on the ground by the end of this parliament in 2020."
Transport Secretary Patrick McLoughlin said his department would be considering the report "in detail".
He said: "As a nation we must be ambitious and forward looking. This is a once in a generation opportunity to answer a vital question."
Local residents have vowed that the recommendation for a third runway at Heathrow is not the end of the story and they will "see it off for good".
Anti-expansion campaigners warn of noise disturbance, air pollution above legal European limits, thousands of people facing eviction from their homes, millions of pounds of public money required to upgrade local roads and a huge environmental battle.
Robert Barnstone, campaign organiser for residents group Hacan said: "This is not the end of the story. The report is published, but we're going to write the final chapter of this report and see it off for good."