Flying at hypersonic Machnumbers using airbreathing propulsion requires highly sophisticated design tools to provide reliable prediction of thrust minus aerodynamic drag to accelerate the vehicle during ascent. Using these design tools, existing uncertainties have to be minimized by a carefully performed code validation process. To a large degree the database required for this validation cannot be obtained on ground. In addition thermal loads due to hypersonic flow have to be predicted accurately by aerothermodynamic flow-codes to provide the inputs needed to decide on materials and structures. Heat management for hypersonic flight vehicles is one of the 'Key-Issues' for any kind of successful flight demonstration. This paper will identify and deal with the role of flight testing during the verification and validation process of advanced hypersonics technology needed for flight in the atmosphere with hypersonic Machnumbers using airbreathing propulsion systems both for weapons and space transport systems. (orig./HM)Available from TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman