Hawaii probably attacked by Japanese flying boats according to the U.S. Joint Intelligence Committee. Daily summary dated 6 March 1942

An item reported that the Japanese aircraft which bombed Honolulu, Hawaii were probably large flying boats. The J.I.C. commented that if it were indeed flying boats these were probably refuelled at sea by submarines.

Source

Map Room Papers (Roosevelt Administration), 1942 - 1945. U.S. Joint Intelligence Committee. Daily summary No. 86 dated 6 March 1942.