Simultaneous double-sided MIG welding as alternative method for joining the skin-stringer T-joints were investigated. The microstructure and mechanical properties of the welded joints were examined. Our study showed that a distance of 27-mm (torch to surface) results in the best weld appearance. Shorter distance produces higher heat input and causes the material stringers to melted with the filler, while longer distance increases the number of porosity and prevents the formation of a complete fusion zone.