On 23 June, the sisters conducted their first catapult training, each with four D4Ys and six E16As aboard; subsequent sessions were conducted on 21 July and 31 August. Two days later, "Hyūga" became the flagship of the Fourth Carrier Division, now commanded by the recently promoted Rear Admiral Matsuda. In September, six racks of 30-tube 12.7 cm anti-aircraft rocket launchers were added. Training of the D4Y and E16A aircrew was slowed by technical problems and was generally conducted from land bases. By 1October the 634th had on strength 17 D4Ys, of which six were serviceable, and 18 E16As, of which 16 were operable.