Ryanair is taking the French government to the European Court of Justice to challenge a ruling that seeks to deny pilots flying from its base in Marseille from operating under Irish contracts.
Under a decree introduced in 2006, Ryanair's pilots and cabin crew operating international routes to and from France are to be subject to local labour law.
Given the generous social welfare benefits in France, this move has the effect of pushing up the costs to Ryanair of employees operating from Marseille.
Ryanair has two aircraft in Marseille, its only base in France (it only flies out of other airports such as Beauvais). The airline is contesting the decree on the basis the crew are working on aircraft registered in Ireland.
France's supreme court, the Conseil d'Etat, has ruled the decree is lawful and rejected a Ryanair request to refer it to the European upper court.
In a statement, the airline said: "Ryanair is confident that the European Court of Human Rights will correct the obvious injustice . . . and allow its employees working on Irish aircraft and on Irish contracts to continue . . . under Irish law."