During World War I, several navies gave consideration to operating scouting aircraft from submarines. The aircraft could extend the search area of the low-lying submarine, which was vital for seeking out merchant ship targets as well as possible threats from warships.
Great Britain, France, Italy, Japan, and the United States experimented with aircraft-carrying submarines between the world wars, but during World War II, only Japan actually employed submarine-launched aircraft—and it did so to a significant degree. Indeed, the only air attack on the continental United States was by a Japanese E14Y “Glen” floatplane from the submarine I-25, which twice carried out bombing missions over Oregon forests in August 1942. (No significant damage was inflicted.)
The largest non-nuclear submarines ever constructed were the Japanese I-400 class, with three boats completed in 1944–45. They were intended to conduct bombing attacks on U.S. cities, with each carrying three floatplanes launched by catapult, but they became operational too late to be used in the war.1
2. This section is derived from Gordon Swanborough and Peter M. Bowers, United States Navy Aircraft since 1911 (Annapolis, MD: Naval Institute Press, 1968), 480.
3. During World War II, these submarines served in the U.S., British, and Polish navies.
4. See N. Polmar and K. J. Moore, Cold War Submarines: The Design and Construction of U.S. and Soviet Submarines (Washington, DC: Brassey’s/ Potomac Books, 2004), 250−54.