The Airports Commission is to publish its final report and recommendations on whether an extra runway should be built at Gatwick or Heathrow.
The options considered were a third runway at Heathrow, extending an existing one, or building a second runway at Gatwick.
The Government is not expected to take any immediate action on the report and is likely to announce that ministers will study the recommendation.
There has been unconfirmed speculation that the report is likely to recommend expansion at Heathrow, but only if the airport meets stringent conditions on air quality, noise pollution and carbon emissions.
Gatwick has argued its expansion would be cheaper and more environmentally viable.
Local opponents of Heathrow expansion say hundreds of thousands more people would suffer from noise and increased traffic congestion.
They say it would also worsen air pollution, from plane fumes and traffic on the M4 and M25 motorways, an issue the Government has already been ordered by the Supreme Court to take immediate action on across the country.
Local residents campaigning against a new runway at Gatwick say expansion there will cause increased noise, pollution, new flightpaths and traffic congestion, hitting the area's heritage and natural landscapes.