This thesis discusses the creation of an object-oriented method to facilitate the creation and specification of aircraft mission profiles. Mission profiles are detailed descriptions of an aircraft's flight path and its inflight mission activities. They are a vital aspect of the conceptual design process of an aircraft. The Mission Profile Input System (MPIS) created is general in nature and can be customized to be compatible with existing aircraft CAD systems. All data associated with the mission—phase parameters, phases, and mission parameters, are defined to be objects. Each data type can therefore be customized individually to meet any requirements which may be necessary to make the MPIS compatible with a host system. Customization of the MPIS is further enhanced by the nature of the design upon which it is based. An object-oriented design provides the system with a high degree of extendibility. The encapsulation and inheritance features of object-oriented design allow new types of phases and phase parameters to be simply "plugged" into the existing system. The MPIS provides the user with an interactive, Motif-like interface which is conducive to manipulating the large quantities of data inherent in specifying mission profiles. The system is based on the ISO graphics standard, PHIGS, and hence is device-independent. Moreover, the system has been implemented using the hybrid object-oriented language, C++, which is supported by a large number of computer systems. / Master of Science