This paper proposes a formalized constraint-oriented approach to structural modeling of assembly units of an aircraft airframe, aimed at supporting the automated selection of an optimal technological process of maintenance and repair. The approach addresses maintenance planning under conditions of limited accessibility, high structural density, and complex spatial configuration of airframe components. The study focuses on the formalization of geometric constraints and design-and-technological properties that determine the parameters of accessibility zones during aircraft maintenance and repair operations. Restrictive properties are represented as parameterized logical-mathematical models describing admissible displacements, feasibility of tool placement and orientation, and interaction between geometric, kinematic, technological, and operational factors. Accessibility zones are modeled as multidimensional feasibility domains governed by logical conditions and technological constraints. An object-oriented approach is employed to represent airframe components, technological equipment, and constraints as interconnected analytical objects with explicitly defined parameters, ensuring scalability and reuse of models across different aircraft configurations. The proposed method enables systematic identification and classification of restricted accessibility zones, objective assessment of technological feasibility, and rational selection of technological equipment at early stages of technological process design. Comparative analysis demonstrates that the developed framework provides higher formal rigor, reproducibility, and automation than conventional geometry-based, expert-driven, and simulation-based methods. The results establish a methodological basis for integration with intelligent CAD systems and digital twin environments, supporting optimization- and AI-driven maintenance planning of complex aircraft airframe structures.