Mayor of London Boris Johnson is considering a proposal to build an airport on the Hoo peninsula in north Kent.
The plan would see the facility built at Cliffe, in an attempt to increase flight capacity around London without extending Heathrow. Other sites under consideration include the Thames Estuary.
Cliffe, which is renowned for its birdlife, was last considered as a site for a new airport in 2002, by the then Labour government. However plans for the site were shelved in December 2003.