The Messerschmitt BF-109G-12 is the trainer version of the Messerschmitt BF-109G. Starting in 1944, some BF-109G-2, BF-109G-3, BF-109G-4, and BF-109G-6's were converted to two seat trainers and designated as BF-109G-12's. A second cockpit was installed for the instructor behind the pilot and a elongated canopy added. The so-called Rustsatze filed modification kits and Umrust-Bausatze factory conversion kits were part of a system promulgated by the RLM throughout the German military aviation industry