Build Variation is a common problem in the Aerospace Industry. Extensive rework is often done to fit critical components and assemblies, with resultant delays in timing and increased costs.Following the Pareto Theory (20% of the parts contribute 80% of the variation) and utilizing Monte-Carlo statistical simulation methods, the assembly is analyzed for build variation. Computer simulation is done incorporating real world part capability data and following the actual assembly sequence.Key contributors to variation are identified by the computer simulation. A core team, consisting of Engineering, Manufacturing, Assembly, Fabrication, and Dimensional Analysis, brainstorm potential improvements. These improvements may be design changes, fabrication changes, assembly changes, or any combination. Several alternatives are considered and re-simulated.Based on the simulation results, the most cost-effective solution is determined that will achieve the dimensional requirements. This solution is subsequently incorporated into the build.