This paper presents a methodological tool which provides to the aeronautical designer a vision for considering the human factors in the aircraft design, focused on maintainability. The main goal of this guideline tool is to orient the engineers to design a product that makes the maintenance tasks easier for people. The guideline comprises a set of tables to drive the engineers for a better evaluation of the design aimed to human factors during the maintenance. It aims at improvements in the technical services to make the maintenance easier with an ergonomic condition. A case study is presented to validate the advantages and benefits achieved when the proposed tool is used.