Japan’s first F-35B fighter jet begins flight testing in Texas before entering service
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As reported by Gherardo Fontana on May 12, 2025, the aircraft designated BX-1, Japan’s first F-35B, conducted its maiden test flight over North Texas. This event marked the beginning of the operational testing process for the Short Take-Off and Vertical Landing (STOVL) variant acquired by Japan, which plans to procure a total of 42 F-35Bs. Japan becomes the fourth country to operate this variant after the United States, the United Kingdom, and Italy. The F-35B procurement is part of a broader Japanese strategy to enhance its ability to conduct air operations from maritime platforms such as modified Izumo-class helicopter destroyers and to increase responsiveness in defense of remote islands.Follow Army Recognition on Google News at this link
In December 2018, Japan formally approved the acquisition of 105 more aircraft, 63 F-35As and 42 F-35Bs, bringing the total planned fleet to 147. (Picture source: Gherardo Fontana)
Japan’s participation in the F-35 program was shaped by its longstanding arms export restrictions, which initially excluded it from development-phase activities. These limitations contributed to a decline in the competitiveness of Japan’s defense industry. Lockheed Martin initially proposed final assembly and maintenance capabilities for Japanese industry and later expanded its offer in October 2011 to include component manufacturing and engine assembly, following U.S. government authorization to share confidential technologies with Japanese firms. On December 20, 2011, the Japanese government announced its intent to procure 42 F-35As for approximately $8 billion, with deliveries to begin in 2016 to replace the F-4 Phantom II. In May 2012, the U.S. Defense Security Cooperation Agency (DSCA) submitted a notification to Congress for a $10 billion Foreign Military Sales (FMS) agreement covering 42 aircraft.
By 2012, Japanese officials indicated that F-35s ordered after fiscal year 2013 would include components manufactured in Japan. In 2013, it was confirmed that Japanese firms would be engaged in producing 24 components, including radar and engine parts. Mitsubishi Electric was tasked with manufacturing seven radar components, IHI Corporation with 17 engine components related to the fan and turbine, and Mitsubishi Heavy Industries (MHI) with manufacturing elements of the rear fuselage, wings, and undercarriage. Four F-35As ordered in 2012 were to be delivered as finished products, while those ordered in 2013 would include Japanese components. The decision to involve local firms as subcontractors allowed Japan to maintain its arms export restrictions without legislative changes, while still participating in production. Insights gained from these activities were expected to contribute to domestic programs such as the Mitsubishi ATD-X.
In 2014, MHI requested government subsidies to support manufacturing F-35 parts for export. Of the original 42 F-35As, the first four units were assembled in Fort Worth, Texas, with the remainder produced at the Final Assembly and Check-Out (FACO) facility in Nagoya. That same year, Japanese Defense Minister Itsunori Onodera confirmed a plan to replace approximately 100 F-15J fighters not selected for modernization with additional F-35 units. In September 2014, the Japanese government also announced plans to develop a domestic stealth fighter to exceed F-35 performance, citing the logistical and strategic advantages of domestically built systems.
By December 2017, the Yomiuri Shimbun reported that Japan was considering modifying the Izumo-class helicopter destroyers to accommodate approximately 10 F-35B fighters. Several options were considered, including the possibility of U.S. Marine Corps aircraft operating from these ships. Chinese government officials expressed concern over the potential move and called for caution. In February 2018, the Yomiuri Shimbun reported that Japan was also evaluating F-35B procurement for the defense of outlying islands, with delivery and operational capability potentially starting in 2024 and 2026, respectively. In November 2018, the Nikkei Asian Review stated that Japan was preparing to order an additional 100 F-35s, including both F-35A and F-35B variants, with the F-35B expected to support ship-based operations. In December 2018, Japan formally approved the acquisition of 105 more aircraft, 63 F-35As and 42 F-35Bs, bringing the total planned fleet to 147.
The F-35B differs from the F-35A by incorporating a Rolls-Royce LiftFan, roll posts on the wings, and a Three-Bearing Swivel Module integrated with the F135-PW-600 engine. (Picture source: US DoD)
Initially, the Japanese Ministry of Defense planned to reduce costs by not assembling the 105 additional aircraft domestically. However, this decision was reversed in 2021 due to reductions in the cost of local production. In April 2019, the United States proposed limited disclosure of the F-35 software source code to Japan as part of Lockheed Martin’s bid to participate in Japan’s next-generation F-3 fighter development. On June 18, 2019, the Japanese Ministry of Defense formally requested that Japan be elevated from customer to partner status in the F-35 program. The request, made by Atsuo Suzuki, director general for defense buildup planning, was addressed to Ellen Lord, then head of U.S. defense acquisition. It sought detailed information on the cost-sharing responsibilities and approval mechanisms associated with partner status. While some U.S. officials supported the request, it was expected to be denied due to the precedent it might set for other customer nations.
In June 2020, Japan Marine United began modifying the Izumo-class helicopter destroyers to operate F-35Bs, confirming the government’s intent to implement fixed-wing operations at sea. On July 9, 2020, the DSCA announced that the U.S. State Department had approved a possible $23.11 billion FMS deal for 105 additional F-35s (63 F-35As and 42 F-35Bs), along with training, support, and spare parts. This was in addition to the initial 42 F-35As and became the second-largest FMS deal ever authorized by the U.S. The DSCA emphasized that the sale would support U.S. strategic objectives in the Asia-Pacific region by strengthening Japan’s air defense capabilities and aiding the replacement of the JASDF’s F-4 fleet. The DSCA noted that the proposed deal would not alter the regional military balance and that Japan would be able to incorporate the aircraft without difficulty.
Detailed annual procurement data from Japanese budget documents shows that the country has steadily funded F-35 acquisitions since FY2012. As of FY2025, Japan has procured 71 F-35As and 27 F-35Bs, with three additional B variants and eight A variants included in the 2025 budget of ¥185.70 billion. The final target is 105 F-35As and 42 F-35Bs. F-35Bs are specifically intended to support STOVL operations from ships and remote locations, while A variants will be used for standard air operations.
The F-35B, developed by Lockheed Martin in cooperation with Northrop Grumman and BAE Systems, is the only fifth-generation fighter with STOVL capability. It is equipped with a shaft-driven Rolls-Royce LiftFan, two roll posts, and a Three-Bearing Swivel Module (3BSM) connected to the F135-PW-600 engine. This system enables vertical landing and short takeoff by managing airflow through the lift fan, roll posts, and nozzle. These elements are mechanically linked to a clutch and shaft assembly from the low-pressure turbine, generating around 30,000 shaft horsepower. The aircraft’s maximum gross weight is 60,000 pounds, though vertical landing is restricted to less than 40,600 pounds. To meet this requirement, aircraft may need to reduce payload or dump fuel prior to landing.
The F-35B’s flight control system supports three major flight modes: CTOL, STOL, and VTOL. STOVL engagement requires weight limits to be met and involves automated adjustments to nozzle angles and airflow. (Picture source: US DoD)
Unlike the F-35A, the F-35B does not have a tailhook; pressing the HOOK/STOVL switch activates STOVL mode. It is structurally limited to a 7-g maneuvering envelope instead of the 9-g capability of the F-35A. The variant’s smaller weapons bay, due to lift system placement, restricts internal payload options. Its external pylons are also subject to reduced load limits, with the outermost stations rated for only 1,500 pounds to prevent fatigue. The F-35B’s refueling method uses a probe system. It has an internal fuel range of approximately 845 kilometers and a full range of around 1,670 kilometers. Thrust-to-weight ratio is 0.90 at full fuel and 1.04 at 50% fuel.
The F-35B’s flight control system supports three major flight modes: CTOL, STOL, and VTOL. STOVL engagement requires weight limits to be met and involves automated adjustments to nozzle angles and airflow. During hover, the aircraft can remain stationary with zero ground speed, adjusting for wind through roll post and nozzle corrections. Vertical landings can be performed with two 1,000 lb Joint Direct Attack Munitions (JDAMs), two AIM-120 air-to-air missiles, and fuel reserve, depending on weight constraints.
Cockpit systems are standardized across all F-35 variants and include a Panoramic Cockpit Display (PCD), touchscreen interfaces, and a Helmet-Mounted Display System (HMDS) that presents flight and targeting data directly onto the visor. The F-35B lacks a traditional HUD, relying instead on the virtual HUD projected inside the helmet. All STOVL-specific controls are integrated into the cockpit’s physical switch set and digital displays. AUTO TO mode automates short takeoff procedures when engaged and within specified weight limits. The aircraft can hover and land vertically with assistance from its onboard flight control computer, using stick and trim inputs for pilot-guided descent.
Japan’s decision to adopt the F-35B is intended to provide flexible airpower options for use in locations with limited runway infrastructure or maritime constraints. The aircraft is designed for expeditionary use and supports interoperability with allied forces. The full suite of avionics includes the AN/APG-81 active electronically scanned array radar, AN/AAQ-37 Distributed Aperture System for infrared threat detection, and AN/ASQ-239 electronic warfare suite. Ongoing software and hardware updates are implemented to address emerging threats and operational requirements. The F-35B’s integration into Japan’s force structure marks a significant shift in airpower strategy, with applications for both ship-based and island-based missions, and aligns with Tokyo’s efforts to diversify deployment options across its geographically dispersed territory.
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As reported by Gherardo Fontana on May 12, 2025, the aircraft designated BX-1, Japan’s first F-35B, conducted its maiden test flight over North Texas. This event marked the beginning of the operational testing process for the Short Take-Off and Vertical Landing (STOVL) variant acquired by Japan, which plans to procure a total of 42 F-35Bs. Japan becomes the fourth country to operate this variant after the United States, the United Kingdom, and Italy. The F-35B procurement is part of a broader Japanese strategy to enhance its ability to conduct air operations from maritime platforms such as modified Izumo-class helicopter destroyers and to increase responsiveness in defense of remote islands.
Follow Army Recognition on Google News at this link
In December 2018, Japan formally approved the acquisition of 105 more aircraft, 63 F-35As and 42 F-35Bs, bringing the total planned fleet to 147. (Picture source: Gherardo Fontana)
Japan’s participation in the F-35 program was shaped by its longstanding arms export restrictions, which initially excluded it from development-phase activities. These limitations contributed to a decline in the competitiveness of Japan’s defense industry. Lockheed Martin initially proposed final assembly and maintenance capabilities for Japanese industry and later expanded its offer in October 2011 to include component manufacturing and engine assembly, following U.S. government authorization to share confidential technologies with Japanese firms. On December 20, 2011, the Japanese government announced its intent to procure 42 F-35As for approximately $8 billion, with deliveries to begin in 2016 to replace the F-4 Phantom II. In May 2012, the U.S. Defense Security Cooperation Agency (DSCA) submitted a notification to Congress for a $10 billion Foreign Military Sales (FMS) agreement covering 42 aircraft.
By 2012, Japanese officials indicated that F-35s ordered after fiscal year 2013 would include components manufactured in Japan. In 2013, it was confirmed that Japanese firms would be engaged in producing 24 components, including radar and engine parts. Mitsubishi Electric was tasked with manufacturing seven radar components, IHI Corporation with 17 engine components related to the fan and turbine, and Mitsubishi Heavy Industries (MHI) with manufacturing elements of the rear fuselage, wings, and undercarriage. Four F-35As ordered in 2012 were to be delivered as finished products, while those ordered in 2013 would include Japanese components. The decision to involve local firms as subcontractors allowed Japan to maintain its arms export restrictions without legislative changes, while still participating in production. Insights gained from these activities were expected to contribute to domestic programs such as the Mitsubishi ATD-X.
In 2014, MHI requested government subsidies to support manufacturing F-35 parts for export. Of the original 42 F-35As, the first four units were assembled in Fort Worth, Texas, with the remainder produced at the Final Assembly and Check-Out (FACO) facility in Nagoya. That same year, Japanese Defense Minister Itsunori Onodera confirmed a plan to replace approximately 100 F-15J fighters not selected for modernization with additional F-35 units. In September 2014, the Japanese government also announced plans to develop a domestic stealth fighter to exceed F-35 performance, citing the logistical and strategic advantages of domestically built systems.
By December 2017, the Yomiuri Shimbun reported that Japan was considering modifying the Izumo-class helicopter destroyers to accommodate approximately 10 F-35B fighters. Several options were considered, including the possibility of U.S. Marine Corps aircraft operating from these ships. Chinese government officials expressed concern over the potential move and called for caution. In February 2018, the Yomiuri Shimbun reported that Japan was also evaluating F-35B procurement for the defense of outlying islands, with delivery and operational capability potentially starting in 2024 and 2026, respectively. In November 2018, the Nikkei Asian Review stated that Japan was preparing to order an additional 100 F-35s, including both F-35A and F-35B variants, with the F-35B expected to support ship-based operations. In December 2018, Japan formally approved the acquisition of 105 more aircraft, 63 F-35As and 42 F-35Bs, bringing the total planned fleet to 147.
The F-35B differs from the F-35A by incorporating a Rolls-Royce LiftFan, roll posts on the wings, and a Three-Bearing Swivel Module integrated with the F135-PW-600 engine. (Picture source: US DoD)
Initially, the Japanese Ministry of Defense planned to reduce costs by not assembling the 105 additional aircraft domestically. However, this decision was reversed in 2021 due to reductions in the cost of local production. In April 2019, the United States proposed limited disclosure of the F-35 software source code to Japan as part of Lockheed Martin’s bid to participate in Japan’s next-generation F-3 fighter development. On June 18, 2019, the Japanese Ministry of Defense formally requested that Japan be elevated from customer to partner status in the F-35 program. The request, made by Atsuo Suzuki, director general for defense buildup planning, was addressed to Ellen Lord, then head of U.S. defense acquisition. It sought detailed information on the cost-sharing responsibilities and approval mechanisms associated with partner status. While some U.S. officials supported the request, it was expected to be denied due to the precedent it might set for other customer nations.
In June 2020, Japan Marine United began modifying the Izumo-class helicopter destroyers to operate F-35Bs, confirming the government’s intent to implement fixed-wing operations at sea. On July 9, 2020, the DSCA announced that the U.S. State Department had approved a possible $23.11 billion FMS deal for 105 additional F-35s (63 F-35As and 42 F-35Bs), along with training, support, and spare parts. This was in addition to the initial 42 F-35As and became the second-largest FMS deal ever authorized by the U.S. The DSCA emphasized that the sale would support U.S. strategic objectives in the Asia-Pacific region by strengthening Japan’s air defense capabilities and aiding the replacement of the JASDF’s F-4 fleet. The DSCA noted that the proposed deal would not alter the regional military balance and that Japan would be able to incorporate the aircraft without difficulty.
Detailed annual procurement data from Japanese budget documents shows that the country has steadily funded F-35 acquisitions since FY2012. As of FY2025, Japan has procured 71 F-35As and 27 F-35Bs, with three additional B variants and eight A variants included in the 2025 budget of ¥185.70 billion. The final target is 105 F-35As and 42 F-35Bs. F-35Bs are specifically intended to support STOVL operations from ships and remote locations, while A variants will be used for standard air operations.
The F-35B, developed by Lockheed Martin in cooperation with Northrop Grumman and BAE Systems, is the only fifth-generation fighter with STOVL capability. It is equipped with a shaft-driven Rolls-Royce LiftFan, two roll posts, and a Three-Bearing Swivel Module (3BSM) connected to the F135-PW-600 engine. This system enables vertical landing and short takeoff by managing airflow through the lift fan, roll posts, and nozzle. These elements are mechanically linked to a clutch and shaft assembly from the low-pressure turbine, generating around 30,000 shaft horsepower. The aircraft’s maximum gross weight is 60,000 pounds, though vertical landing is restricted to less than 40,600 pounds. To meet this requirement, aircraft may need to reduce payload or dump fuel prior to landing.
The F-35B’s flight control system supports three major flight modes: CTOL, STOL, and VTOL. STOVL engagement requires weight limits to be met and involves automated adjustments to nozzle angles and airflow. (Picture source: US DoD)
Unlike the F-35A, the F-35B does not have a tailhook; pressing the HOOK/STOVL switch activates STOVL mode. It is structurally limited to a 7-g maneuvering envelope instead of the 9-g capability of the F-35A. The variant’s smaller weapons bay, due to lift system placement, restricts internal payload options. Its external pylons are also subject to reduced load limits, with the outermost stations rated for only 1,500 pounds to prevent fatigue. The F-35B’s refueling method uses a probe system. It has an internal fuel range of approximately 845 kilometers and a full range of around 1,670 kilometers. Thrust-to-weight ratio is 0.90 at full fuel and 1.04 at 50% fuel.
The F-35B’s flight control system supports three major flight modes: CTOL, STOL, and VTOL. STOVL engagement requires weight limits to be met and involves automated adjustments to nozzle angles and airflow. During hover, the aircraft can remain stationary with zero ground speed, adjusting for wind through roll post and nozzle corrections. Vertical landings can be performed with two 1,000 lb Joint Direct Attack Munitions (JDAMs), two AIM-120 air-to-air missiles, and fuel reserve, depending on weight constraints.
Cockpit systems are standardized across all F-35 variants and include a Panoramic Cockpit Display (PCD), touchscreen interfaces, and a Helmet-Mounted Display System (HMDS) that presents flight and targeting data directly onto the visor. The F-35B lacks a traditional HUD, relying instead on the virtual HUD projected inside the helmet. All STOVL-specific controls are integrated into the cockpit’s physical switch set and digital displays. AUTO TO mode automates short takeoff procedures when engaged and within specified weight limits. The aircraft can hover and land vertically with assistance from its onboard flight control computer, using stick and trim inputs for pilot-guided descent.
Japan’s decision to adopt the F-35B is intended to provide flexible airpower options for use in locations with limited runway infrastructure or maritime constraints. The aircraft is designed for expeditionary use and supports interoperability with allied forces. The full suite of avionics includes the AN/APG-81 active electronically scanned array radar, AN/AAQ-37 Distributed Aperture System for infrared threat detection, and AN/ASQ-239 electronic warfare suite. Ongoing software and hardware updates are implemented to address emerging threats and operational requirements. The F-35B’s integration into Japan’s force structure marks a significant shift in airpower strategy, with applications for both ship-based and island-based missions, and aligns with Tokyo’s efforts to diversify deployment options across its geographically dispersed territory.
