People's Liberation Army Navy vessels (PLAN) increasingly make incursions in the Western Pacific Ocean via the Miyako Strait. The Miyako Strait is one of the few international waterways through which China can access the Pacific Ocean. There is also increased Chinese naval and aerial activity near the Senkaku islands which are owned by Japan, but claimed by China. This puts the Southern Ryukyu Islands at the forefront of Japan's national defense. By 2030 China could have four aircraft carriers. Meanwhile, Japan only has two relatively small Izumo-class carriers. Each Izumo can carry just 10 F-35s. There are currently no plans to build bigger multi-purpose operation destroyers though experts say Japan needs at least four carriers for effective use in real combat situations.