Originally completed as seaplane tenders the Chitose and Chiyoda were converted into carriers after the Battle of Midway. The original ships were specially designed to facilitate later conversion.
The Chitose and Chiyoda were ordered under the 1931 - 1932 Supplementary Program.
To help with stability large bulges were added.
There were two elevators that served a single hangar.
There was a mix of oil and diesel turbines. The diesel allowed for long range, and the oil for speed.
There were one / two hangars. The hanger was 300' long.