Her conversion and work up completed by the end of June 1942, "Un'yō" made three voyages from Japan to Truk, Saipan, and Rabaul between July and October. From late October to early January 1943, she ferried aircraft from Japan to the Philippines, Palau, the Dutch East Indies and Truk. "Taiyō" began transporting aircraft from Japan to Formosa and Truk at the beginning of November. "Chu'yō"s conversion was finished in November 1942 and she spent the next year exclusively ferrying aircraft to Truk, usually in company with one or the other of her sisters. "Chu'yō" and "Taiyō" were in company on 24 September 1943 when the latter was torpedoed; "Chu'yō" had to tow her to Yokosuka as one propeller shaft had been damaged by the torpedo hit. "Chu'yō" herself was torpedoed by the submarine on 4 December; the hit blew off her bow and she had to steam in reverse. The submarine torpedoed her twice more later that day and disabled her engines. The third attack finally caused her capsize with heavy losses.