The Boeing Model 204 was an American biplane, pusher configuration flying-boat aircraft built by Boeing in 1929. Externally, the 204 looked identical to the Boeing Model 6E, but a number of internal changes, including increasing the passenger capacity to four, gave it a new type certificate and model number.
Construction was started on five aircraft, but only two were completed. The first, designated 204 and the second 204A. A third aircraft was built by a private owner who had bought the three incomplete machines. The 204A was a dual-control version which was later owned by Peter Barnes, who flew it on his private Seattle-Victoria, British Columbia main run.
The C-204 Thunderbird, a modified 204, was the first type produced by Boeing Aircraft of Canada. These had altered wing and tailplane incidence and a reduction in upper wing area. The prototype was first flown on 30 March 1930, the first of a batch of four. They failed to sell readily, though they were sometimes leased for work. Eventually three were sold. All worked in British Columbia, remaining active until 1939.