RYANAIR HAS dropped its High Court challenge to the aviation regulator's decision to make Dublin airport slot co-ordinated for the summer 2007 season, which ran from March to October.

Ryanair's legal action was withdrawn on Wednesday. The airline declined to comment yesterday on its reasons for pulling the case but said it would publish a statement today on the matter.

In a statement, aviation regulator Cathal Guiomard welcomed Ryanair's move. "The withdrawal by Ryanair of their legal challenge brings to a conclusion their bid to overturn the Commission [ for Aviation Regulation's] decision to designate Dublin airport as co-ordinated," he said.

"At the court's direction, Ryanair is obliged to pay the legal costs incurred by the commission to date in the defence of this challenge."

It is not clear how much Ryanair will have to pay to meet the regulator's legal bill but sources indicated that it could be between €50,000 and €100,000.

The regulator made his decision in February 2007. This was the second time that he had sought to introduce slot co-ordination at Dublin Airport.

The move is aimed at regulating competition for aircraft slots at peak times when demand is greater than capacity. It replaced a voluntary system and has remained in place since the end of the summer 2007 travel season.

Slot co-ordination has been consistently opposed by Ryanair, the biggest user of Dublin airport, which has argued that the airport is not congested.

The low-fares airline successfully blocked Mr Guiomard's attempt to make Dublin co-ordinated in 2005 when the High Court ruled the regulator's consultation process was flawed. That ruling is currently the subject of an appeal to the Supreme Court.

The allocation of slots at Dublin is managed by Airport Co-ordination, a British company that carries out similar tasks at Heathrow, Gatwick and Stansted airports.

No comment was available from the Dublin Airport Authority but it had previously welcomed the move by the regulator.