The Japanese cabinet has approved a plan to add an additional 105 Lockheed Martin F-35s to its planned fleet of 42 examples, potentially making it the world’s second largest F-35 operator.

In a press briefing, the chief cabinet secretary Yoshihide Suga confirmed that the country’s Medium Term Defence Program has been approved by the cabinet.

Of Tokyo’s eventual F-35 fleet of 147 examples, it is likely that 107 will be conventional take-off and landing F-35As, while 40 will be short take-off and vertical landing (STOVL) F-35Bs. Flight Fleets Analyzer shows that a fleet of this size would make Tokyo the second largest operator of the F-35 type after the United States, and putting it ahead of the United Kingdom.

The news follows extensive media reports in November stating that Tokyo would beef up its F-35 acquisition, and add F-35Bs to the mix.

There is no timeline to build the fleet to this level, but production would almost certainly take place at Mitsubishi Heavy Industries’ F-35 final assembly and check-out facility at Nagoya.

Flight Fleets Analyzer shows that the Japan Air Self Defence Force has taken delivery of nine F-35As from the original 2011 order for 42.

The first Nagoya-produced F-35A rolled out in June 2017. From 2019, it is expected to produce six examples annually. IHI, which makes the Pratt & Whitney F135 locally, will produce six engines a year to support the MHI line.

The original batch of F-35As is replacing Tokyo’s fleet of F-4 Phantoms, which are being phased out.

Recent media reports suggest that the additional F-35s will replace about 100 Boeing F-15s that are unviable for upgrading. Flight Fleets Analyzer shows that the Japan Air Self Defence Force has 155 F-15Js and 45 F-15DJs, the average age of which is 30 years.

The F-35Bs will operate from the Japan Maritime Self Defence Force’s pair of Izumo helicopter carriers, which will be modified to operate jet aircraft. One media report says it is possible that ramps may be included to assist the launching of aircraft.

Suga pegged the cost of overall acquisitions over the next five years to Y27 trillion ($239 billion), up 11% from its previous five-year plan announced in 2013. Other elements of the new five-year plan include four KC-46A tankers, and nine Northrop Grumman E-2D Hawkeyes.

Japan’s decision to obtain additional F-35s comes amid increasing tensions in north Asia, particularly with China. Beijing has steadily built up advanced capabilities in both the aerospace and maritime domains.

“The security environment is getting severe,” says Suga. “This plan needs to be implemented quickly.”