It's a classic landmark planning battle — with conflicting environmental and economic arguments vying against each other.

Supporters of the airport extension cite financial benefits, not just in terms of investment but in strengthening business trip options. They also list leisure market benefits in terms of increased holiday destination routes.

But objectors stress the deep concerns about the environment and health impacts on residents living close to the airport and under flight paths.

George Best Belfast City Airport lodged its planning application to lengthen the runway 590m in the direction of Holywood in November 2008. The opposition is led by Belfast City Airport Watch, a coalition of residents’ groups and individuals.

It believes the runway extension would lead to 6,000 more flights a year, planes landing and taking off closer to Holywood, bigger jets flying over homes, schools, parks and workplaces, an increase in the number of flights taking off over the city, lower take-offs and greater traffic congestion in east Belfast.

Belfast City Airport Watch has called for a public inquiry to examine all the issues.

It is understood a decision on whether the public inquiry will go ahead could be made within weeks.

However, George Best Belfast City Airport believes such a move would not establish any further facts about the controversy.

It has consistently offered reassurances in response to the concerns being raised by residents and environmental organisations.

The airport has denied larger planes will use the runway and said that as the number of flights or air traffic movements through George Best Belfast City Airport is governed by a planning agreement, it is restricted on the number of air traffic movements possible in any 12 consecutive months. The proposed runway extension would not alter the planning agreement, it has argued.

The airport says operating hours will not be affected if the extension goes ahead and the number of flights over the city will not increase.

Among those who have publicly supported the runway extension over recent months are Mike Smyth, an economist at the University of Ulster, economist John Simpson, Howard Hastings, chair of the Northern Ireland Tourist Board, Professor David Carson from the University of Ulster, Joanne Stewart from the Institute of Directors, Glyn Roberts from the Northern Ireland Independent Retail Trade Association and Terry Hoey, chairman of Palmerston Road Residents Association.

Peter Dixon, group chief executive of Phoenix Natural Gas, has also pledged his support to the planned extension.