High Quality Content by WIKIPEDIA articles! The Dornier Do X was the largest, heaviest, and most powerful flying boat in the world when it was produced by the Dornier company of Germany in 1929. First conceived by Dr. Claudius Dornier in 1924, planning started in late 1925 and after over 240,000 work hours it was completed in June 1929. Only the Tupolev ANT-20 Maxim Gorki Russian landplane of a few years later was physically larger between the two World Wars, but was not as heavy as the Do X, at 53 metric tons maximum takeoff weight versus the Do X`s 56 tonnes.