Rhön-Rossitten Gesellschaft
The Rhön-Rossitten Gesellschaft (RRG) or Rhön-Rossitten Society was a German gliding organization, the first one in the world that was officially recognised. The Rhön-Rossitten Gesellschaft was mainly responsible for establishing gliding as a sport, not only in Germany but eventually throughout the world.
Source: Wikipedia — Rhön-Rossitten Gesellschaft (CC BY-SA 4.0)