Aircraft mass and inertial properties are required for predicting the dynamics and handling qualities of aircraft. However, such properties can be difficult to estimate since these depend on the external shape and internal structure, systems, and mass distributions within the airframe. Mass and inertial properties of aircraft are often predicted using computer-aided design software, or measured using various experimental techniques. The present paper presents a method for quickly predicting the mass and inertial properties of complete aircraft consisting of components of constant density. Although the assumption of constant density may appear limiting, the method presented in this paper can be used to approximate mass properties of complex internal structures. Inertial estimates for rectangular cuboids, cylinders, spheres, wing segments, and rotors are presented here. The influence of geometric properties of wing segments such as sweep, taper, airfoil geometry, and dihedral are included. The utility of the method is presented and the accuracy is evaluated with various test cases.