The challenges of hypersonic system development require a combination of integrated ground testing, flight testing, and computational/simulation approaches. This report addresses the role of flight testing in the triad of development approach and is sub-divided into three parts: Propulsion, Aerothermal and Extrapolation of ground test data to flight. The reasons for propulsion flight test are illustrated by specific mini-case studies. The second part reviews some of the fundamental issues of flight testing and provides an overview of the aerothermal techniques. Specific examples include heat-transfer gage measurements and some of the common problems that have been encountered. The third part of this report discusses the initial flights of the Space Shuttle which uncovered a number of differences between preflight aerodynamic predictions and actual flight data. Most notable among these discrepancies was for longitudinal trim during high-speed re-entry. To investigate these differences, several computer codes were applied to a modified Space Shuttle Orbiter to determine aerodynamic parameters over a wide range of conditions. Computations were carried out for wind tunnel conditions and flight conditions to assess Mach number, real gas, and viscous effects on the reentry aerodynamics of the orbiter. flight-testing, Aerothermal techniques, Hypersonic vehicles, Computational Fluid Dynamics (CFD) simulations, High-speed re-entry.