A secret deal was reached at the earliest stages of the Izumo program to design the ships to be modular enough for conversion into a vessel that could carry F-35B aircraft, according to a JMSDF executive who also spoke with the news outlet last week.
Two Izumo-class ships, JS Izumo and JS Kaga, are already primed for F-35B operations, even though the country hasn't pulled the trigger on a purchase of the STOVL-capable jets. A Japanese official recently confirmed that a purchase of 25 F-35As — the jet's traditional runway variant — is in the pipeline but a decision on F-35B aircraft has not been reached.
While Washington and Tokyo maintain close defense ties, the F-35A was originally designated as the primary US export-variant joint strike fighter, with the UK as the lone exception. Downing Street has committed to buying 138 F-35Bs, the Financial Times reported last November.
Japanese Defense Minister Itsunori Onodera has denied that any "specific efforts" were being made to customize Izumo warships to handle F-35B operations. "No concrete examination is under way on the introduction of F-35B or remodeling of Izumo-class destroyers," the minister told reporters in December.
The Izumo-class warships are the largest navy ships Japan has produced since the end of World War II. One of the ship's primary competitive advantages is its ability to carry Japan's most advanced anti-submarine warfare (ASW) helicopters, the Diplomat notes. However, Izumo ships carrying F-35Bs would have somewhat diminished ASW capabilities, defense analysts have said.