This paper presents the flight test results of a fully adaptive algorithm for autonomous fixed wing aircrafts landing developed by CIRA, the Italian Aerospace Research Centre. The algorithm is designed and implemented in the framework of a complete autonomous guidance system, worked out by CIRA, able to allow autonomous way-points navigation, autonomous landing and autonomous collision avoidance for fixed wing aircrafts. The algorithm presented in the paper is designed to perform a fully adaptive autonomous landing starting from any point of the three dimensional space, based on the use of the DGPS/AHRS technology. Main features of the autolanding system based on the implementation of the proposed algorithm are: on line landing trajectory re-planning, fully autonomy from pilot inputs, weakly instrumented landing runway, ability to land starting from any point in the space and autonomous management of failures and/or adverse atmospheric conditions. The flight tests have been conducted at an airfield in Caserta, in the south of Italy, close the CIRA. The paper is structured into several paragraphs describing the algorithm designed for the autolanding maneuver, the control system architecture and the methodologies developed in order to safely manage the possible presence of failures and/or unfavorable weather conditions, the preliminary results of the real time validation with hardware in the loop simulation and, finally, the performances achieved by using the CIRA experimental flying platform, with reference to the real flight experiments. Nomenclature X = position along X-Runway axis ) ( X V X = inertial velocity profile along X-Runway axis ) ( X V Z = inertial velocity profile along Z-Runway axis ) ( X H = position profile along Z-Runway axis 0 H = initial position along Z-Runway axis 0 X = initial position along X-Runway axis 0 X V = initial inertial velocity profile along X-Runway axis F H = desired final position along Z-Runway axis F X = desired final position along X-Runway axis XF V = desired final inertial velocity profile along X-Runway axis ZF V = desired final inertial velocity profile along Z-Runway axis