This report describes the implementation of an airspace complexity server into the preindustrial prototype of the Extended ATC Planner. First, there is the description of the current ATC en-route control room situation, with a presentation of the different actors and their roles. Then, a study of the multi-sector planner (EAP) is made, focused on the frame of the new SESAR operating method. The third part of the report deals with the airspace complexity. It is defined, then the algorithms are detailed and its applications for the EAP are justified. Finally, there is the description of the airspace complexity implementation in the EAP prototype. The platform and complexity server architectures are presented, simulations and results are analysed and future improvements are proposed in order to continue the project later on.