Heinkel He 111 Z (Zwilling) :This was a design that entailed the merging of two He 111s. The design was originally conceived to tow the Messerschmitt Me 321 glider. Initially, four He 111 H-6s were modified. This resulted in a twin-fuselage, five-engine aircraft.10 were produced and five were built from existing H-6s.It could tow a Gotha Go 242 glider or Me 321 for up to 10 hours at cruising speed. They were also planned as heavy bombers.