The looming retirement of the P-3 Orion and the subsequent loss of capability, potentially impose a serious limitation on Asia-Pacific security. This paper aims to detail the initial design conception for a maritime patrol UAV to complete this role. Through a brief analysis of the history of maritime aircraft and their roles, specifically focused on the potential benefits of utilising UAVs over their manned counterparts, a list of realistic engineering requirements is able to be generated. This paper will also discuss the development of these specifications into a concept aircraft for the final thesis paper. This will be conducted using a generic design process outlined by Dr Jan Roskam in the Airplane Design series in combination with DARcorps Advanced Aircraft Analysis software. This design method is capable of generating an operational and performance envelope, structural envelop and complete stability and control model. Results from analysis will be validated with historical data of similar aircraft.