Around 10,000 farmers, former residents, ecologists, politicians and local officials are to rally in Notre-Dame-des-Landes to "reoccupy" the 1,700 hectares of agricultural land
where the airport is to be built.
Ayrault, who was mayor of Nantes from 1989 until he became prime minister, is an enthusiastic supporter of the airport.
The airport project’s supporters believe it is necessary to replace the Nantes Atlantiques, which they say has reached saturation point and is poorly situated.
Opponents say the 550-million euro project, which allows the Vinci company control for 55 years, is ecologically harmful and unnecessarily expensive and that Nantes Atlantiques could be expanded.
Work on transport access is due to start in 2013 and on building the airport itself in 2014.
For several months about 150 anti-capitalist campaigners, some from Spain and Germany, have been camping in disused farmhouses, cabins and tree houses on the site.
There have been several clashes with the police.
Local officials said that police would not try and stop the rally, which was not banned, but would intervene if the law was broken.