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The Douglas O-5 was an observation aircraft based on the Douglas World Cruiser, the aircraft that made the first successful circumnavigation of the globe.
In the early 1920s several countries made attempts to carry out staged flights around the world. A British attempt in 1922 failed, as did a French team in 1923. In the same year the US Army Air Service also began to consider an attempt, and searched for a suitable aircraft. It would need a long range, and interchangeable land and water undercarriages. Douglas was asked to provide data on its Davis-Douglas Cloudster, but instead chose to push a modified version of the US Navy's Douglas DT-2 torpedo bomber. This was a single bay biplane with rear-folding wings, interchangeable wheels and floats. The Air Corps decided to order the construction of a single prototype of the new Douglas World Cruiser, the first time the Army purchased a Douglas design.
The DWC was very similar to the DT-2, but its range was extended by removing military equipment and installing six times as much fuel. The new aircraft had one 60 gallon tank in the centre section of the upper wings, one 62 gallon tank in the root of each lower wing, a 150 gallon tank behind the engine fire wall, a 160 gallon tank below the pilot and a 150 gallon tank below the observer. This meant the aircraft could carry 644 gallons of fuel and had a theoretical maximum range of 2,200 miles.
The DWC was powered by the same 420hp Liberty engine as the DT-2, but had a modified radiator system with the facility to swap between small and large radiators depending on the local climate.
On 1 August 1923 General Patrick, Chief of the Air Service, approved the design and an order was placed for a prototype. This aircraft was completed with great speed and had passed its service trials by the time the flight was approved on 19 November 1923.
On 27 November an order was placed for four aircraft (later named Seattle, Chicago, Boston and New Orleans). The last of these was delivered on 11 March 1924. Spare parts were placed at fixed points on the route, and on 4 April 1924 the four aircraft left Seattle at the start of their epic journey.
The Seattle was forced to pause for repairs in Alaska, and was lost when it crashed into a mountain while attempting to catch up with the other three (both crewmen survived). The aircraft travelled via Yokohama, Korea, China, Hong Kong, Thailand, Burma, India, the Middle East, south and central Europe. From Paris they went to London, then to Brough near Hull. Their trans-Atlantic trip began at Scapa Flow, and seen afterwards the Boston was forced to put down at sea. It was found by the cruiser USS Richmond, and was towed towards the Faroe Islands, but sank one mile from safety. The surviving two aircraft safely reached Seattle on 28 September, at the end of a record breaking 28,945 miles flight.
The USAAS then placed an order for six military versions of the design. This used the same basic structure as the DWC, with interchangeable wheels and floats, but with only 110 gallons of fuel and twin 0.3in machine guns in the observer's cockpit. They were originally designated as Douglas Observation Seaplanes (DOS), but in May 1924 became the Douglas O-5. The O-5 was used by the 2nd Observation Squadron, at Kindley Field Corregidor, part of the Philippine Aviation Department.