Electric aircraft makes aviation more efficient and sustainable. Experimentally demonstrated hybrid and fully electric aircrafts require high voltage electric systems and high-power density machines for their commercial usage. Insulation life time of these electrical systems should be substantial to make these designs feasible for commercial aircraft applications. While insulation degradation due to the aeronautical environment on high voltage cables are heavily researched, impact on winding insulation is not investigated. Life time of motors significantly depend on the winding insulation quality. This paper presents the insulation qualification analysis and its impact on life time for a form-wound air-core armature winding using partial discharge (PD) test. The windings that were tested and presented in this paper are designed using Litz-wire for a high-speed 1MW permanent magnet synchronous motor(PMSM). In this paper, special attention is given to the high altitude operating condition of the machine and the PD tests are performed under those conditions. These results are used to investigate the impact of voltage induced stress on the life time of the machine. Temperature and pressure variation and its impact on PD activity on the implemented windings insulation scheme are experimentally tested.