Following "Sea Lion's" postponement in October 1940, the "Luftwaffe" decided in the fall of 1941 to continue producing Siebel ferries apart from the Army under its Special Ferry Command ("Fähre-Sonderkommando"). It replaced the diesel truck engines on the original design with BMW and other type aircraft engines, housing four of them in enlarged pontoon ends connected to water screws via a reversing gearbox. Some of these vessels were assigned to the Army and operated with mixed crews, but the Army disliked the use of aircraft engines, claiming they were prone to catching fire and consumed excessive amounts of fuel. The Army Engineer Ferry Construction Command at Antwerp continued using vehicle engines as the main propulsion unit, and considered them reliable compared to the "Luftwaffe's" aircraft engines. Ten were built for Operation Herkules, although it was cancelled.