Around 200 people protested in the rain against the closure of Filton Airfield near Bristol on Saturday.
The airfield is owned by BAE Systems, which plans to close it at the end of the year.
BAE wants to use the land for an “aerospace enterprise zone”.
Unite argues this will cost jobs, as 2,500 houses will be built over part of the site.
Dave Tiley, a local councillor and chair of the aerospace branch of the Unite union, helped organise the event.
He said, “This is a fantastic show. We’ve defied the weather and our critics.
“We are here to fight to save it so let’s hope we make a difference. We need jobs and manufacturing, not just houses.”