The aim of the research is to explore the applied benefits of Gas Path Analysis (GPA) in Gas Turbine Performance Diagnostics with the main objectives of the implementation of measurement noise and leakage model on GPA analysis. Thereupon, the final outcome will be the investigation of the impact of measurement noise on performance diagnostics, the statistical analysis of the results, and the examination of GPA capabilities on leakage fault diagnostics. The analysis of the research tasks conducted with Rolls Royce Trent 500 high bypass turbo-fan engine model by using TURBOMATCH simulation code.