Use of Lighter-Than-Air (LTAs) vehicles for the telecommunication and surveillance purposes has attained a great deal of interest in recent years. This platform is very attractive because of its long endurance and cost effectiveness. The shape of airship envelope has huge impact on its performance. Literature suggests that shape of the airship should be such that it should have significant maneuvering capabilities and stability in the stratosphere. This paper presents open loop and closed loop stability analysis of Gertler shape of stratospheric airship which has minimum circumferential stresses and minimum drag characteristics. The complete 6-DOF nonlinear mathematical model of Gertler shape has been developed for the analysis of stability. As airship is a buoyant vehicle, added mass effect is taken into account while deriving the equations of motion. Stability analysis is carried out using the linearized model at a desired operating condition using both time domain and frequency domain techniques. Different motions of the airship with its control characteristics is explained at the end of paper. This analysis is to be used to develop Guidance, Navigation and Control (GNC) strategy for the stratospheric airship.