Currently organizations are investing large sums of money, time and knowledge to stay competitive and profitable. Driven by strong competition and increasing operational costs, the global aviation industry is under paramount pressure to strengthen operational excellence and improve profitability. Airlines are heavily investing in the means to improve productivity and reduce variation in the maintenance, repair and services processes. Both the well-established and new entrees to the aviation industry need to develop and implement well-developed and proofed quality management system to stay competitive and lead the industry and/or expand to new market segments. A quality management system will help Airlines to meet their customers’ expectation through improved products and services. Ethiopian Airlines (EAL) is facing fierce market competition from European and Middle East airlines such as KLM, Turkish Airlines, Emirates, Qatar and Fly Dubai. EAL implemented Achieving Competitive Excellence (ACE) to improve its performance and stay competitive in the market. ACE is a custom-made system developed by United Technology Cooperation (UTC) and yet not proved useful in other organizations. Its implementation highly depends on organizational culture, company resource and existing quality management system. To understand and exploit advantage of ACE, a detailed investigation of its philosophy, tools, techniques, critical success factors, pre-conditions and (dis-)advantages is established. Furthermore, a detailed comparison and potential benefits of its integration with the well-established quality improvement system Six Sigma, are demonstrated. Six Sigma is a business process improvement approach that seeks to find and eliminate causes of defects and errors, reduce cycle time and cost of operations, improve productivity to meet customer expectations, and achieve higher asset utilization and returns. Six Sigma employs a project-based method that uses statistical and non-statistical tools and techniques to remove process variation and improve process performance and capability. Furthermore, Six Sigma is a data-driven, result oriented and uses well-trained improvement specialists and top-down approach to execute the improvement processes. To thoroughly understand the logical reasoning behind ACE and to improve the rate of ACE implementation, resemblances between ACE and Six Sigma and benefits of integrating of ACE and Six Sigma on organization performance; the main research question is formulated as: “How can Six Sigma be integrated with Achieving Competitive Excellence (ACE) quality management system to reduce products and services variance, and to improve the performance of an organization?” An extensive literature review on business performance, Six Sigma and ACE is carried out to establish a theoretical framework for this research project. The literature finding of ACE is demonstrated with an exploratory case study at EAL. A detailed insight to the practical challenges and barriers of ACE implementation are presented. The findings of the literature review are crafted against the case study in corporation with ACE experts to formulate firm conclusions and recommendations. Organizations must thoroughly identify their strategy, structure and culture, institutional forces, resources and performance measurement system before embarking on ACE and Six Sigma integration. Top management involvement, commitment and leadership is critical for successful integration. A top-down approach is suggested for project prioritization and selection in an integrated Six Sigma and ACE environment. This increases the involvement of top management in continuous improvement processes. Top management translates organization’s strategies to goals and objectives to meet customers’ expectation and remove barriers and obstacles to enhance efficiency and effectiveness of continues improvement programs. Furthermore, top-down approach facilitates integration of stakeholders’ issues; sustained profit, low operational cost, sustainable annual growth and usage of “voice of customer” (VOC) as an input to project selection process. The introduction of Design for Six Sigma (DFSS) in design and development of new products and services leads to sustainable business operation in a dynamic market environment by delivering high quality products and services to their customers with at lower-cost. DFSS benefits ACE with by reducing product development cycle and high production efficiency and effectiveness. Six Sigma’s tools like design of experiment (DOE), analysis of variance (ANOVA), linear regression analysis, multivariate SPC and other improve process certification process and reduce process variation. The benefits of these tools further extend to problem solving and decision making through relentless root cause analysis. Thus, ACE and Six Sigma integration extends the benefits of these tools to ACE. In cooperating environment/ community and employee’s satisfaction perspectives in the existing balanced scorecard (BSC) extends business performance measurement to more dimensions. The new perspectives together with BSC‘s four perspectives are smoothly translated to ACE Control Tower six categories at strategic level. This helps to track, monitor and evaluate the effect of ACE or integrated Six Sigma and ACE on organization strategies and performance. An Action-learning model facilitates understanding the current situation and employee’s perceptions and involvement in an improvement process. The model helps organizations to bring organizational change and to create a clear understanding of current situation. Action-learning model play a great role in bringing paradigm shift from result-oriented to means driven culture and in developing safe practice field to support network (community of practice) of fellow employees. A well-structured Cell formation guideline that defines the number of employees per Change Agents per Cell, ways to weight operational activities in a Cell and ability to solve conflicts of interest between sections in a Cell must be developed. To reduce employees’ turnover and internal transfer, an incentive or compensation plan for those Cells with excellence business performance must be put in place. Moreover, organizations should create knowledge management system to capture the tacit knowledge from senior quality management experts. The integration makes ACE more data and fact driven, execute process certification on project basis with top-down approach, total value chain gets more focus, improve new products and services design and increased employees and suppliers involvement and get other benefits.