When the Japanese planes take off for Pearl Harbor, some of the 3 man torpedo planes only have a pilot.
The code for successful surprise (and the movie's title) "Tora! Tora! Tora!" was a shortening of the words totsugeki (attack) and raigeki (the Japanese term for torpedo bombers), and was originally spelled "To ra, to ra, to ra!" Those two shortened words were interpreted by American radio operators, who happened to intercept them, as the Japanese word for "tiger"; hence "Tora! Tora! Tora!"