This thesis focuses on the development of a proof-of-concept design, modelling, and motion planning for a mobile snake robot for aircraft wing box assembly. For design, several concepts have been explored against the requirement that the robot would move from station to station and mimic a human arm to reach inside the wing box through an access hole to install fasteners. The final design is a P1R4 snake robot along with an end effector socket allowing for alignment compliance when the tool engages with a fastener. For modeling, forward kinematics is formulated using the DH method and verified with a PoE approach. An analytical solution for inverse kinematics is found. For motion planning, first path planning is carried out from the robot locking position to the entrance point of the access hole, and then entering inside the wing box to reach the desired fastening target locations. Second, trajectory generation is realized using MATLAB ppval function and collision detection is performed using MATLAB inShape function, which generates a natural cubic spline interpolation from a given set of waypoints prescribed from the wing box CAD data and ensures no pose collisions by using MATLAB cylinder2P and alphaShape functions. The planned path is verified through simulation using MATLAB Simscape. The case study simulation results show that the snake robot can access about 95.4% of the interior of the wing box to perform the required fastening operation. In conclusion, this thesis work has demonstrated the feasibility of the proposed method.