Northern Ireland's two main airports are squaring up for a legal battle which could have a major bearing on which of them gets control over its skies.

TBI, the company which owns Belfast International Airport at Aldergrove, has launched a High Court action against Belfast City Airport at Sydenham over its proposed £20 million sterling (€32.6 million) terminal.

Welsh-based TBI is seeking a judicial review of planning approval for the new terminal at Sydenham, owned by Canadian aerospace company Bombardier-Shorts.

Work is already underway on the new terminal and associated airport facilities and Bombardier-Shorts hopes to have them open for business by the end of this year.

TBI's challenge is based on environmental concerns. The company claims in court papers that, in granting planning approval, the Department of the Environment failed to comply with European directives about conserving natural habitats.

The papers also claim the Department failed to impose any conditions safeguarding adjoining areas of Special Scientific Interest and a Nature Reserve.

The court action is the latest move in a lengthy and bitter battle between the airports. In 1995, Belfast International tried to buy its rival for £28 million but was blocked by the Monopolies and Mergers Commission.

The granting of planning permission led Mr Paul Kehoe, chief executive of Belfast International, to claim the decision had been "rushed through" when power was transferred to the Assembly.

Belfast City Airport countered by accusing its rival of "sour grapes" and said the proposal had been through a lengthy and laborious planning process lasting 10 months.

Before the judicial review can be heard, a judge has to grant leave to proceed. Yesterday Mr Justice Kerr adjourned the application for leave until March 10th.