Extreme environments like active volcanoes exhibit many difficulties in being studied by in situ techniques. For example, during eruptions, summit areas are very hard to be accessed because of logistics problems and/or volcanic hazards. The use of remote sensing techniques in the last 20 years by satellite or airborne platforms has proven their capabilities in mapping and monitoring the evolution of volcanic activity. This approach has become increasingly important, as much interest is actually focused on understanding precursory signals to volcanic eruptions. In this work we verify the use of cutting-edge technology like unmanned flying system thermally equipped for volcanic applications. We present the results of a flight test performed by INGV in collaboration with the University of Bologna (Aerospace Division) by using a multi-rotor aircraft in a hexacopter configuration. The experiment was realized in radio controlled mode to overcome many regulation problems which, especially in Italy, limit the use of this system in autonomous mode. The overall goal was not only qualitative but also quantitative oriented. The system flew above an Italian mud volcano, named Le Salinelle, located on the lower South West flank of Mt. Etna volcano, which was chosen as representative site, providing not only a discrimination between hot and cold areas, but also the corresponding temperature values. The in-flight measurements have been cross-validated with contemporaneous in-situ acquisition of thermal data and from independent measurements of mud/water temperature.