The giant Messerschmitt ME.321 glider was originally conceived to carry tanks, guns and men for the invasion of the United Kingdom. Even after Operation Sealion was cancelled there was still thought to be a need for it for the forthcoming invasion of the Soviet Union.
Both Messerschmitt and Junkers submitted a similar design, but the Junkers Ju.322 proved a failure and was abandoned. The first flight on 25 February 1941 proved successful (towed into the air by a Ju.90) resulting in a contract for 100 Me.321A-1 production machines (later supplemented by a similar number of Me.321B-1s.
The usual towing aircraft in service was generally the Heinkel He.111Z
