Insufficient attention to long-range bombers forced the Luftwaffe command in the middle of World War II to look for other ways of striking long-range targets. One of these options was the Mistel strike composite aviation complex. The idea was to make one of the aircraft of the complex a kind of large guided projectile, the second aircraft (located on top) took over the control functions. The strike aircraft was supposed to be a conventional bomber. In it, instead of the cockpit, a huge warhead with an explosive charge weighing about 1800 kg was mounted. The planes had to fly in a coupler, and the control plane could receive fuel from the tanks of the lower plane. In the Mistel 1 variant, the control plane was the Messerschmitt Bf 109F-4 fighter, and the attack plane was the Junkers Ju 88A-4 bomber. The training version of the complex for practicing control and guidance methods received the designation Mistel S1