Abstract: The Reynolds number effect is a major challenge that hinders designing large aircraft. This paper first introduces the Reynolds number effect from the perspective of large aircraft design and development, along with a comprehensive overview of the research progress. Subsequently, the influence of the Reynolds number effect on aerodynamics is discussed, focusing on its law and mechanism of influence, on the high-speed, low-speed, and component aerodynamic designs of large aircraft. The research progress on flow mechanism associated with the Reynolds number effect is also presented. Furthermore, several strategies to address the Reynolds number effect are outlined, including advanced wind tunnel testing technologies, data correction methodologies, and the integration of artificial intelligence in the Reynolds number correction process. Lastly, this paper concludes with a summary of the key findings related to the effects of Reynolds number and insightful recommendations for future research in this area.