This dissertation is based on the internship I realized in Alstom, where my objective was to analyse the evolutions of the client demand. It is structured around three main sections: the first one presents the problem, the second one the major concepts which are important to know to understand the situation of the production plant. The last chapter presents the difficulties Alstom Le Creusot has to face because of frequent modifications in the client demand. Here are also presented the reasons why the rolling stock (Alstom’s client) changes his demand, the consequences it has on all the departments and potential solutions to improve the responsiveness of the production plant.