Designed by Dr. Claudius Dornier, the Dornier Do-X was the largest and heaviest flying boat in the world upon its completion in 1929, with a wingspan of 157 feet and a maximum takeoff weight of more than 61 tons.

The massive aircraft was financed by the German Transport Ministry, but it was built in Switzerland, on the shores of Lake Constance, in order to comply with terms of the Treaty of Versailles, which forbade Germany from building certain classes of aircraft.

The Do-X was powered by a dozen engines mounted in a tandem “push-pull” configuration atop the wing, which could just barely haul the hulking craft up to an altitude of 1,650 feet. True to its boat-like design, the Do-X's complex engines were not directly controlled by the pilot — the captain in the cockpit had to send orders for throttle adjustments to a flight engineer in the engine room.