I-10′s Yokosuka E14Y1 (Allied reporting name "Glen") floatplane began reconnaissance flights over ports in South Africa by reconnoitering Durban on 20 May 1942, followed by flights over East London, Port Elizabeth, and Simon's Town over the next week. On the night of 29 May, the plane flew over Diego-Suarez, Madagascar, sighting the battleship among the ships anchored there. The "A" detachment commander selected Diego-Suarez as the target for a midget submarine attack, scheduled for 30 May 1942. I-16 and I-20 launched their midget submarines off Diego-Suarez on 30 May, but I-18′s midget suffered engine failure and she could not launch it.
