The project is a technical study for a Wide Area Multilateration System for the Flight Information Region of Vilnius. The Vilnius FIR covers all the Lithuanian territory. The objectives of the project are to study the Multilateration Systems, in specific the WAM Systems to be able to develop different solutions applied in the particular case of Lithuania. The environment of work is very important in this type of studies, and the surroundings of the FIR and the operational issues are taking into account. The methodology used is based on a theoretical analysis of the systems, for the understanding of the properties and capabilities of each segment of the system. An evaluation is made to guide the results to be reasonable. Some comparisons are elaborate, particularly between the MLAT and SSR systems. The final solution is focused in the type of system, the architecture, the location of receivers in the territory, commercial solutions available and costs. Finally, conclusions of the project are made, with an environmental mention about benefits and problems of this system deployment.