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. The Do X was financed by the German Transport Ministry and built in a specially designed plant at Altenrhein, on the Swiss portion of Lake Constance, in order to circumvent the Treaty of Versailles which forbade any aircraft exceeding set speed and range limits to be built in Germany after World War I. While the type was popular with the public, a lack of commercial interest and a number of non-fatal accidents prevented more than three examples from being built.
First conceived by Dr. Claudius Dornier in 1924, planning started in late 1925. Construction work started on 19 December 1927, and the Do X was completed in June 1929, after over 240,000 work hours.
Launched on 12 July 1929, the Do X immediately began taxiing trials. These soon led to 122 flights conducted over the following six months, during which time the aircraft was briefly grounded, to allow replacement of the original Bristol Jupiter engines by Curtiss Conquerors. The most notable of these flights occurred on 31 October 1929, when the Do X set a maximum take off weight record by taking to the air while carrying 10 crew, 150 official passengers and nine stowaways!