Changes to a Bill this week mean a civilian airport is unlikely to be developed at Baldonnel aerodrome.

The Aer Corps base is seen by some as the best possible location for a second large airport in Dublin.

Any commercial development at the military base would require planning permission. In addition, civilian air movements would have to be regulated by the Irish Aviation Authority. But a change this week to the Aviation Regulation Bill, which establishes the office of Aviation Regulator, means the jurisdiction of authority will not expand to include military air space.

The change was proposed by the Minister for Public Enterprise, Ms O'Rourke, at the Oireachtas Joint Committee on Public Enterprise and Transport. Ms O'Rourke's spokesman said the question of developing a civilian airport at Baldonnel was for the Department of Defence to decide.

Only one plan to develop a civilian operation at Baldonnel has emerged. Ryanair's founder, Dr Tony Ryan, has proposed a corporate jet base at the military aerodrome, though the plan has never reached an advanced stage.

The proposal to expand the Irish Aviation Authority's jurisdiction was to facilitate the development of a flight training school at the Aer Corps camp at Gormanston, Co Meath.

It is understood that separate legislation is now seen as the best means of facilitating this longstanding project.