In this thesis we present basics of GNSS navigation and it's use in flight navigation. We present global satellite navigation systems and description of determination of receiver's postition on base of code observations. Determination of receiver's position is base for other tasks of navigation. In next part we are describing basic terms and concepts in general navigation and in flight navigation. At the end we are describing use of GNSS navigation in aviation. Described are basic principle of GNSS navigation during all phases of flight – approach, landing and take-off. Practical use of GNSS navigation during approach, landing and take-off is illustrated with it's use at Graz International Airport.