Up to a thousand demonstrators are expected to gather in a field near Gatwick this weekend.
They're planning to reveal a one hundred foot sign protesting against proposals to change the airport's flight paths.
While many could see fewer planes flying over them others could see more and that will prove highly controversial.
The move will lead to the current flight path map being ripped up and redrawn and should also see delays cut, less fuel burnt and emissions reduced.
It is part of a new directive from Europe to simplify and make airspace more efficient and cope with increasing demand. It is not connected with the current review of runways by Sir Howard Davies.
But the move could allow for half a million more planes over the south east a year in a thirty year period. That is the Government forecast to allow for passenger growth.
Some flight paths could be altered or moved altogether. At the moment flight paths are over a wide area.
Using new technology there could be more accurate routes with increased numbers of flights concentrated on them. That means fewer planes flying over a wider area and more on the new routes.