Business leaders from 36 organisations in the South East are taking a letter to 10 Downing Street arguing the case for expansion at Gatwick Airport.
They said a second runway would create tens of thousands of jobs and add £1.7bn a year to the local economy.
Campaigners against the idea have claimed it would cause "unacceptable" levels of pollution.
The government is due to make a final decision over whether Gatwick or Heathrow should expand this summer.
Last July the Airports Commission recommended a third runway at Heathrow as its chosen solution.
The organisations have a combined membership in excess of 15,000 businesses who, it is estimated, employ more than 100,000 people.
Jeremy Taylor, of Gatwick Diamond Business, who co-ordinated the support for the letter said: "This is the clearest indication the prime minister needs that the next runway for the country should be built at Gatwick.
"It is the cheapest and most deliverable option that causes the lowest impact of the schemes under consideration.
"Those who oppose have made a lot of noise for a very small number of people; the quiet majority now feel it is their turn to be heard."