The event was organised by Stop Heathrow Expansion (SHE) and Friends of the Great Barn to protect Harmondsworth, which originated as a Saxon manor.
"I was so pleased to see the Heathrow villagers rallying to our campaign to save the village once more.
"The Harmondsworth open day demonstrated what a beautiful village would be lost if the third runway went ahead."
The parliamentary candidates stopped for photos to reiterate their stand against a possible third runway at Heathrow.
Alick Munro, Green candidate for Hayes & Harlington, said: “As a GP with patients in Harlington, I am daily made aware of the effects of air pollution. About one in three of my patients asks for help to cope with their cough, even although the prevalence of smoking in the area is low.
"Nitric oxide and small particle pollution from traffic fumes are well known to make runny nose and itchy eyes worse and aggravate the results of lung function tests.”
A focus of the event was the reopening of the 15th-century Great Barn since the completion of major repairs by English Heritage.
Poet Sir John Betjeman described the barn as “the cathedral of Middlesex”, which was saved from developers by the intervention of a group of determined villagers.
Neil Keveren, chair of Stop Heathrow Expansion (SHE), said: “This is a chance for us to show to the world that we are utterly determined to fight for our homes and our community. We will not be going anywhere else.”
The event included the unveiling of a giant mural on Cambridge Close, especially created for the open day, to illustrate the proposed airport boundary cutting through the village.
Mr Keveren added: “We are thankful for the backing we have received from Hillingdon Council and from Harts, the community arts project”.
As well as displaying the mural, SHE and HARTS set up a tree-planting planting project in the Heathrow Villages, with the first tree planted in Harmondsworth Recreation Ground on the day.
World War Two RAF veteran Tommy Thomas, who is one of the oldest residents of the village at age 93, was chosen to plant the oak tree.
As well as the oak, nine new trees now form a triangular grove just south of Harmondsworth primary school.
The Airports Commission has been examining potential sites for new runways in the South East and is expected to publish its final report in June.
SHE hopes to take the canvas on its folding frame to various locations before the Davies Commission announces its recommendation.