Diorama of the German Lufthansa (DHL), Motherships for airplanes in the South Atlantic, since 1934

In the beginning, the idea was to build an air mail service from Europe to South America with the help of scheduled airliners in order to reduce the previous mail transit times from at least 3 weeks (from Berlin to Buenos Aires in 1934) to a few days. The airplane material at that time could not make such a long non-stop-flight, and so a concept was developed that worked well and worked until the outbreak of the new World War: 

The DLH Junkers Ju 52 airliners carried the mail across Spain to Bathurst in West Africa, later sometimes Heinkel He 111 airliners were deployed.  There the cargo was reloaded on flying boats such as Dornier Wal (until 1937), later Dornier Do 18 or even later on the float plane Blohm & Voss Ha 139. These planes should take over the Atlantic route from Bathurst / West Africa to Natal / Brazil.

 In Brazil, the cargo was reloaded again onto Ju 52s of national companies and then distributed to the recipient cities. Depending on the weather conditions, the ships in Brazil also met the planes halfway on their flight route. 

Since the range of the aircraft for the long flight West Africa to Brazil or vice versa was not enough, the idea of ​​an aircraft mother ship was conceived: A flying boat loaded to the limit was hoisted on board and placed on a (Heinkel) catapult. With the help of this steam catapult the heavy plane was quickly airborn, thus not wasting its fuel in the starting procedure, but put it into distance. Often the ships with the aircraft on board sailed a few hundred kilometers in direction of the destination.

The ships had another special feature: the so-called tow sail, which was laid out at the stern of the ship on the water to calm the waves before the aircraft could be hoisted on board after landing. The aircraft had to "roll"- say swim - on this tow, then the on-board crane could do its work on the calm plane. 

The first ships were converted freighters, which received a catapult and a crane system with the tow sail. These were the“Schwabenland” and the “Westfalen”. In 1936, the newly designed               “Ostmark”was built in Kiel and put into service from the end of May. About 300 flights were organized from 1936 - 1939 when the war broke out. 

The Ostmark moved to the neutral country of Portuguese Guinea for about one year, but was then supposed to join the service of the German Air Force at home. Nothing came of it, because on September 24, 1940 off the French coast it was sunk by  a British submarine.

Except for one man, the crew could be saved. The wreck was discovered in 2002 by French divers.