Like the DC-4, DC-6 and Constellation,Flying boats occupied a unique period of time in aviation, primarily between the two world wars, as the desire and technical ability to carry greater payloads across greater distances became ever greater. Prior to WW2, there were few runways in the world with sufficient length to launch a transoceanic aircraft, but large bodies of water were of course plentiful and offered a huge opportunity to launch flying boats from. Of course, WW2 also brought with it the construction of myriad airfields to support bombers on both sides which post-war, were quickly converted to civilian airports. The runways built to support bomber during the war, and mostly built close to major cities, meant that the writing was on the wall for the demise of flying boats, as it was only a matter of time that aircraft (like the DC-4, DC-6 and Constellation) manufacturers started designing large airliners that demanded paved, longer runways- but for a few short years, the Golden Age of flying boats produced some of the most interesting aircraft designs of the 20th century. The last Boeing 314 Clipper sank in 1951.
,Imperial Airlines as the precursor of BOAC and then much later British Airways needed aircraft with which to service Britain's far flung colonies, and for this, the aircraft company, Stirling Brothers built 31 of the Empire C class flying boats. Two of these, the Cambria and Caledonia, were lightened and equipped with extra tanks so that they could make the trip across the Atlantic and even once visited my hometown of Sarnia, landing in the bay at Windsor after giving Sarnians a tantalizing flyover and announcing the coming era of transatlantic flight one fall day in 1937.
1Not to be outdown by the British, Boeing developed a large flying boat, the Boeing 314 Clipper which was a large flying boat capable of crossing the Atlantic and Pacific oceans, but primarily for very wealthy Pan Am customers only. Known for it's distinctive design. only 12 were built, the last withdrawn from service in 1946 and sadly, none survive- but it was beautiful aircraft and it's distinctive design forever tied it to the romance of travel to farflung destinations. The fact that it could make these extremely long distance flights safely was instrumental in building the confidence people would need to make the transition from boat to airplane in the postwar years.