Protests were expected to mark the start of a planning hearing today on a proposed new runway for Dublin airport.
Residents opposed to the planned 3,000-metre runway insist it will damage the quality of life of some 10,000 people living nearby.
The €150 million project has already been given the green light by Fingal County Council, but objections to An Bord Pleanála by 15 parties led to an oral appeal hearing.
Green Party leader and Dublin North TD Trevor Sargent is among those who lodged their opposition to the development by the Dublin Airport Authority.
The hearing, beginning this morning at the Gresham Hotel on Dublin's O'Connell Street, is expected to run for several days.
This morning, Teresa Kavanagh, of community group United Portmarnock Residents Opposing Another Runway (Uproar), said the planned runway would be used by jumbo jets and posed a number of health and safety issues.
"We have to remember we have a population of four million. We have three State airports. There are runways lying idle in Shannon and Cork," she told RTÉ's Morning Ireland. "This is a lop-sided development, it goes against decentralisation and sustainability, and it's not in the national interest.
"It's about the privatisation of Dublin Airport down the road, that's what it's about."
Bob Hilliard, of the Dublin Airport Authority, insisted on the same programme that community concerns had been addressed in the proposals.
"The most important thing to remember is this is part of an overall development plan for the airport, including a second terminal, that's going to deal with the growth in demand for air travel, and that runway has actually been in the county development plan for 35 years," he said.
"Of course, the community nearby us have concerns and we have put forward a range of community measures to try and mitigate any impact the runway may have on people, particularly those who are very close to it."
Aircraft will mostly take off, or land, to the west of Portmarnock to decrease any impact on residents, according to Mr Hilliard.