Aichi M6A Seiran

The Aichi M6A Seiran was a specialized attack floatplane developed for the Imperial Japanese Navy during World War II, designed to be launched from large I-400 class submarines for surprise, long-range strikes. While intended to attack the Panama Canal or U.S. mainland, the planes never saw combat, with the mission being canceled upon Japan's surrender. 
 
Key Details on Intended Use and Operational Status:
Submarine Deployment: The M6A1 was built to operate specifically from the I-400, I-401, I-13, and I-14 submarines.
Targeting: The primary target was initially the Panama Canal (Gatun Locks) to cut off U.S. supply lines, later changed to the U.S. naval base at Ulithi Atoll.
"Operation Cherry Blossoms at Night": There were proposed plans to use these aircraft for biological attacks on the U.S. West Coast, though this was never implemented.
Operational History: The planes were ready for deployment in summer 1945, but the war ended before they could attack. Upon Japan's surrender, the planes on the I-401 were ordered to be destroyed or ditched at sea, with one surviving example now on display at the Smithsonian. 
 
The M6A1 could be stored in a pressurized hangar on the submarine, with wings and tail folding to allow for quick assembly and launch, typically within seven minutes.