Light gliders had already proven their worth in the Gernman attack on Fort Eben-Emael in Belgium (the first ever assault by gliderborne troops), and would later be used successfully in the Crete invasion in 1941. However, the prospect of mounting an invasion across the English Channel focused minds on the need to be able to airlift vehicles and other heavy equipment as part of an initial assault wave.


In 1940, German aircraft designer Willi Messerschmitt developed the idea of ‘tank-carrying gliders’ to be used in the projected invasion of Britain. When the ‘Me 321 Gigant’ glider first appeared at the front, it produced tremendous astonishment. With a wingspan of 55 metres, it could carry up to 22 metric tons of freight: fuel, ammunition, trucks, tanks, 200 fully equipped troops and more.


Towing such a large glider was an engineering challenge. The Luftwaffe conceived the idea of joining two existing bombers by a central wing. Ernst Heinkel answered the call. The Zwilling Tow Plane In 1941, two prototypes of the He-111Z (Z=zwilling=twin) were produced using the airframes of four He-111H-6 bombers.

The He-111Z used the fuselages of two He-111H’s complete with tail assembly joined by a center wing section mounting three Junkers Jumo 211 engines.

The Zwilling proved to be extremely efficient and had power to spare while towing the gigantic gliders. For additional take-off power, JATO rockets could be mounted beneath each fuselage and under the center wing section.


The twinned aircraft carried a crew of seven. The pilot sat in the port fuselage, with five throttles, full instrumentation, controls for the port undercarriage, and radiator flaps for the three engines on his side. The second pilot in the starboard fuselage was given dual controls but no throttles, and worked the starboard undercarriage and two sets of starboard engine radiator flaps. It was not easy to control in flight, but it enjoye a trouble-free career.


Although the Me 321 saw considerable service in Russia as a transport, it was never actually used for its intended role as an assault glider.  Eight of the twelve Zwillings were destroyed in service, shot down by fighters or destroyed as a result of bombing. The remaining four were presumably destroyed after surrender.

In 1941, the Luftwaffe produced a motorized variant of the Me 321. Six French Gnome-Rhone GR14N engines were fitted to it and it was called the Me 323. It was something of a ‘sitting duck’, being so slow and large an aircraft. No Me 323’s survived in service beyond the summer of 1944.