Junkers G.38

The Junkers G 38 was a German airliner of the early 1930s, designed according to Hugo Junkers’ philosophy of thick, load-bearing wings. Operated by Deutsche Luft Hansa on European routes, it introduced advanced solutions such as passenger cabins integrated into the wings. Built in only two examples, it remains one of the most ambitious civil aircraft projects of the pre-war period. Source Wikipedia