Continuous technological development and increasing efficiency demands are driving products toward becoming more and more complex. For the aerospace industry - where the requirements for performance, safety and low environmental impact already are substantial - this means that more extensive quality assurance measures must be taken to ensure the fulfillment of the requirements of each individual component.However, to avoid that the work with quality improvement become too extensive and increase the product cost to unbearable levels it is necessary to have methods to prioritize and focus improvement efforts on the product features that matters most for fulfilling customer requirements. Therefore, the concept of Key Characteristics is used today, both in the aerospace and other industries; a term for those characteristics that have a significant impact on requirement compliance and whose outcomes at the same time are expected to vary considerably in manufacturing.The concept itself is similar among those who use it but the purpose of and methodology for identifying and managing Key Characteristics vary, even within the same industry. This thesis is therefore aimed to create a view of which factors that characterize an effective and efficient way for companies in the aerospace industry to work with Key Characteristics. The thesis involves a case study to create a framework for how companies within this industry work with Key Characteristics, a literature review to see which approaches are advocated by previous research and two benchmark studies to see examples of how Key Characteristics are used and handled in practice in industry.The results show that the work of Key Characteristics should meet three main criteria in order to be effective and efficient: • it must be clearly focused on the characteristics that have critical impact on customer requirements and at the same time considerable variation in production, • it should be initiated early in the product development process and then performed iteratively during the process of continuously reducing variation problems in manufacturing, and • it should identify Key Characteristics using both qualitative and quantitative tools to best capture all different kinds of requirements on the product.Finally a practical example is given of how the work with Key Characteristics should look like at GKN Sweden AB, the case study company in the aerospace industry, to effectively minimize the costs associated with production variation, and yet satisfy all customer requirements.