Discussed is the development of two computer programs for the calculation of cross-sectional areas for existing aircraft and aircraft concepts. The first program allows the user to display aircraft described in Hess format, to restructure the data in a manner compatible with computational fluid dynamic codes for predicting viscous flow drag, and to compute and display the axial distribution of cross-sectional area normal to the free-stream airflow. The second program is an extension of an existing conceptual design code called ACSYNT /VPI. The extension allows calculation of areas of intersection between a cutting plane tilted at an arbitrary angle with the aircraft axis and the aircraft. The design of both codes is described in depth, and user's guides for the resulting programs are included in the appendices. / Master of Science