The European Commission has blocked Ryanair's £600m deal to acquire Aer Lingus citing competition concerns.
"The Commission's decision protects more than 11 million Irish and European passengers who travel each year to and from Dublin, Cork, Knock and Shannon. For them, the acquisition of Aer Lingus by Ryanair would have most likely led to higher fares," said EU Competition Commissioner Joaquín Almunia in a statement. He said the remedies were "simply inadequate to solve the very serious competition problems which this acquisition would have created on no less than 46 routes."
The commission, the EU's executive body, threw out an earlier merger bid in 2007, saying a merger would create a monopoly of Irish flights.
Ryanair has vowed to fight the decision in courts.