This presentation covers results out of the European Project (5th Framework) "Welding of Airframes by Friction Stir - WAFS generated in the Workpackage 2. This workpackage dealt with the friction stir welding (FSW) of thin section aluminum (1-6mm). The main objective was to get a better understanding of welds accomplished by FSW especially with regard to mechanical and corrosion properties of the joints. Welding and characterizing similar and dissimilar joints achieved this. The characterization included non-destructive, mechanical and corrosion testing. In order to cover all alloys and their combinations, ten WAFS-partners are involved in the welding and testing. For certain alloys it is already known that an improvement of the properties of the welds is needed. Therefore the development of a cooling system and the usage of pre/post treatments were investigated. In order to introduce this welding process for airframe structures, an analysis on repair methods and design criteria was addressed. This work was divided into 5 sub-workpackages and some of the results obtained will be presented.