Geometrical variation and deviation in all the manufacturing processes affect the quality of the final product. Therefore, geometry assurance is an important tool in the design phase of a new product. In the automotive and aviation industries where the use of composite parts is increasing drastically, new tools within variation simulations are needed. Composite parts tend to deviate more from nominal specification compared to metal parts. Methods to simulate the manufacturing process of composites have been developed before. In this paper, we present how to combine the process variation simulation of composites with traditional variation simulations. The proposed method is demonstrated on a real complex subassembly, representing part of an aircraft wing-box. Since traditional variation simulation methods are not able to capture the spring-in and the special deviation behavior of composites, the proposed method adds a new feature and reliability to the geometry assurance process of composite assemblies.