Bay of Bengal area attracted attention of Japanese naval aircraft according to the U.S. Joint Intelligence Committee. Daily summary dated 31 March 1942

An item reported that there were indications that Allied shipping in the harbour of Calcutta, British Indies would be the a potential target for attacks by Japanese naval aircraft now concentrating in the Bay of Bengal area.

Source

Map Room Papers (Roosevelt Administration), 1942 - 1945. U.S. Joint Intelligence Committee. Daily summary No. 111 dated 31 March 1942