Ranked among the top ten international destinations, Marrakech benefited from the treaty of open skies that Morocco signed a few years ago, thus large numbers of low cost airlines fly to Marrakech from different European cities. Thus, the cost of a trip to Marrakech from Paris, Brussels, Marseilles, Madrid, Lille, Milan, Amsterdam, and Frankfurt can start from 50 Euros.
Here is a listing of partner airlines/flight booking companies:

www.jet4you.com (France, Belgique, Italie...)
www.easyjet.com (Espagne, France...)
www.Atlas-blue.com (France, Belgique, Allemagne, Hollande, Angleterre, Italie etc...)
www.ryanair.com (Allemagne, France ....)
www.govoyage.com (Toute provenance)
www.flug.idealo.de
www.expedia.fr
www.iliva.com
www.vueling.com
www.airarabia.com