Indo-Pacific Region (Agencies) August 7, 2025 — In a significant step toward deepening bilateral defense cooperation, British and Japanese carrier-based F-35B jets are conducting joint operations at sea as part of Operation Highmast, the next phase of the Royal Navy’s Carrier Strike Group 25 deployment. The week-long exercise marks a milestone in UK-Japan air-sea integration, focusing on interoperability and combined maritime strike capabilities in the Indo-Pacific.
Both nations operate the F-35B, a short take-off and vertical landing (STOVL) variant of the fifth-generation stealth fighter. The UK has fielded the aircraft operationally since 2018, while Japan is in the early stages of integrating the platform into its maritime forces following recent upgrades to its Izumo-class helicopter carriers.
According to the UK Ministry of Defence, this week’s operations will see British and Japanese aircraft and crews exercising side by side from sea, enhancing tactical coordination and laying the groundwork for future joint missions. The exercise is expected to strengthen mutual understanding of carrier-based operations and refine procedures for integrated air tasking.
Following the joint phase, the UK task group will divide: HMS Prince of Wales and her escorts will continue to Japan, while other elements will proceed to South Korea, continuing the UK’s broader strategy of persistent presence in the region.
The UK and Japan have steadily expanded their air-sea cooperation. In 2024, Lieutenant Commander Baker, a British F-35 pilot, made history by landing on a Japanese Maritime Self-Defense Force (JMSDF) vessel—the first such landing by a UK pilot. The flight, conducted under the U.S. Patuxent River Integrated Test Force, symbolized growing trust and technical alignment between the two navies.
Japan’s adaptation of its Izumo-class carriers to support F-35B operations involved structural reinforcements and heat-resistant deck coatings, enabling vertical thrust landings and takeoffs. The current joint operations with the UK Carrier Strike Group are viewed as a key opportunity to validate these modifications and expand Japan’s maritime strike capabilities.
Operation Highmast is part of the UK’s Indo-Pacific tilt, a long-term strategy aimed at reinforcing security partnerships through practical exercises, logistics integration, and multilateral deployments. The joint F-35B operations underscore the UK’s commitment to regional stability and Japan’s evolving role as a maritime power capable of forward-deployed air operations.
As both nations continue to modernize their naval aviation capabilities, this week’s exercise serves as a blueprint for future collaboration in high-end maritime warfare and integrated deterrence.