Gatwick airport is studying options to build a second runway.
A second runway cannot be built at London's second largest airport, which moves around 34 million passengers a year through its two terminals, before 2019 under a long-standing local agreement.
However, bosses at Gatwick, owned by Global Infrastructure Partners, said they were now looking at the implications of building a new runway.
They plan to evaluate the environmental, surface access and economic impacts of various runway options.
Relevant environmental issues will include noise and air quality impacts on local communities.
London's Heathrow hub - the capital's busiest airport - is operating close to full capacity after the government blocked development of a third runway when it came to power in 2010, as further expansion of the west London site would mean a huge increase in the number of planes flying directly over the capital.
A commission chaired by former Financial Services Authority head Howard Davies to analyse ways to expand airport capacity in southeast England will report in the summer of 2015 after releasing an interim report next year.
"There are clear practical advantages of a new runway at Gatwick," said Gatwick chief executive Stewart Wingate.
"When compared with a third runway at Heathrow, we would have a significantly lower environmental impact whilst adding significantly more capacity.
"The process of evaluating the runway options will be complex.
"I am committed to undertaking a comprehensive and in-depth assessment that considers not only the economic benefits but also the environmental impacts."
South-east of London, Gatwick is a point-to-point airport, mainly focused on the leisure market, whereas rival airport Heathrow operates as a hub with around a third of its customers being transfer passengers.
Building a second runway at Gatwick could transform it into an international hub.
Earlier this year Wingate said Gatwick would need a second runway to cope with an expected 30 percent rise in passenger numbers over the next 20 years.