Dornier Do X

 The Dornier Do X was a centre-hulled airliner. At the time, 1929, it was by far the largest aircraft in the world. In November 1930, the Do X left Lake Constance for a flight to the Americas via Amsterdam, Calshot and Lisbon. It was built in only three units, the two examples built for Italy were powered by FIAT A.22Rs. Source wikipedia