FROM fire-fighting helicopters to model railways, it will all be on show this Sunday at Ballarat Airport's Open Day.More than 35 community groups and businesses will take part in the free event, from 10am to 4pm.Ballarat 4WD Club members Anne and Peter Bullard founded the open day and, with help from the City of Ballarat, initiated this year's event.Airport manager John Hartigan said up to 5000 people were expected to attend."Everyone in the airport complex will have displays," he said.Mr Hartigan said it had been three years since the last open day and people would be surprised at the development taking place.A variety of aircraft will be on display including the historic Avro Anson and other ex-military aircraft.