The Boeing 314 Clipper was a long-range flying boat produced by the Boeing Airplane Company between 1938 and 1941. One of the largest aircraft of the time, it used the massive wing of Boeing’s earlier XB-15 bomber prototype to achieve the range necessary for flights across the Atlantic and Pacific Oceans.
Twelve Clippers were built for Pan Am. Three of them were sold to BOAC during the Battle of Britain (1940) and delivered in early 1941. (BOAC's 3 Short S.26 transoceanic flying-boats had been requisitioned by the RAF).
http://en.wikipedia.org/wiki/Boeing_314
A replica was built at Foynes Flying Boat Museum. None of the originals do exist.