Japan's ocean liners designed for carrier conversion

Could a navy build large liners in peacetime for conversion into carriers during war?

Yes. Japan required liners to include features for easier wartime carrier conversion, though its naval air service could not expand fast enough to exploit the additional hulls fully.

Japan arranged for ocean liners to be built with features that would make conversion to carriers easier. The government required the merchant operators to anticipate those wartime conversions. The resulting ships could add flight decks, but effective use also required a naval air service able to expand rapidly. Japan's difficulty expanding that service limited what the converted hulls could achieve.