New measures restricting airlines' use of "hush kits" to reduce noise from aircraft come into effect tomorrow across the EU.

A Dublin company owned by the businessmen Ulick and Desmond McEvaddy, Omega Air, has initiated proceedings in the European Court against the change, which it claims will cost it $36 million (€39.7 million euros) in the next five years.

The new regulation has been vigorously opposed also by the US, which claims it discriminates against American companies who might seek to sell aircraft to EU airlines.

In its capacity as a member of International Civil Aviation Organisation (ICAO), the UN-sponsored body which regulates all aspects of civil aviation throughout the world, the US wrote to each of the EU's 15 member-states, also ICAO members, last March complaining about the measure. Under ICAO rules, the EU states are not obliged to respond for 12 weeks after they receive the complaint from the US.

Opposition by the McEvaddy brothers to the measure was the subject of political controversy last summer when it emerged that the Tanaiste, Ms Harney, and the Minister for Finance, Mr McCreevy, had stayed at a holiday villa owned by Mr Ulick McEvaddy in the south of France during holidays.

This was criticised by the Labour Party leader, Mr Ruairi Quinn, who said there could be a perceived conflict of interest as the brothers had sought the support of the Government for its opposition to the EU measure. The McEvaddys rejected the allegations, saying the issue was not before the Government. It would be decided by the European court.

The introduction of the regulation on aircraft noise, which is opposed by the US, means that EU airlines will be prevented from registering older aircraft whose engines have been modified - with hush kits - to reduce noise. The regulation does not apply to modified aircraft which have already been registered. New aircraft adhere to the noise levels permitted by the EU.