<p>The innovation of the current work is to quantify the influence of the uncertain inflow conditions in flight tests. The data and statistical characteristics of main inflow parameters containing uncertainties directly extracted from flight test measurements like typical parameters such as total pressure and total temperature are displayed and discussed for the first time. In contrast to prior studies, our research has been conducted by using real measurement data, yielding qualified results that are of direct and significant value for engineering applications. An uncertainty quantification (UQ) method called non-intrusive polynomial chaos expansion (NIPC) is introduced. The flight test uncertain inflow condition data are from a test conducted at an altitude of about 7000 meters. Similarity transformation is introduced to build a bridge between high-altitude atmosphere and ground environment inflow. The sensitivity analysis (SA) has quantified the importance of total pressure and total temperature to the aerodynamic performance of the NASA Rotor 37. The results show that near-stall condition is the most sensitive to the uncertainties. Since the relative standard deviation of mass flow rate is about 0.45%, which is much higher than that of the uncertain inflow total pressure and total temperature. The effect of uncertain inflow conditions grows as the observed flow domain gets closer to the shroud. The sensitivity rank of aerodynamic performance parameters is the mass flow rate&gt;the total pressure ratio&gt;the isentropic efficiency. The uncertain inflow condition affects most the upper 50% span flow field, especially the 10% span in the top region. The separation flow on the suction side and the tip clearance flow vortex interacting with the shock wave are the critical factors that induce the inflow condition fluctuation to propagate in the flow passage.</p>