What Happened to F-35B Lightning II?
The F-35B Lightning II is the Short Take-Off/Vertical Landing (STOVL) variant of the F-35 Joint Strike Fighter, designed for use by the U.S. Marine Corps, the UK Royal Navy and Royal Air Force, and other international partners. It has achieved significant operational milestones since its Initial Operational Capability in 2015, with ongoing upgrades to its Technology Refresh 3 (TR-3) and Block 4 configurations to enhance its combat capabilities and address evolving threats, despite facing persistent challenges with costs, software development, and recent operational incidents.
Quick Answer
The F-35B Lightning II continues to be a cornerstone of 5th-generation air power for the U.S. Marine Corps, UK, Italy, and Japan, with a focus on integrating advanced Technology Refresh 3 (TR-3) and Block 4 upgrades to boost its lethality and survivability. As of August 2026, the UK has completed its first tranche of 48 F-35Bs (with 47 operational), and Japan has commenced F-35B deployments to its Nyutabaru Air Base. However, the program still grapples with high costs, software delays, and recent incidents, including a crash in California in July 2026 and reports of some USMC F-35Bs flying without radar due to upgrade delays.
📊Key Facts
📅Complete Timeline13 events
X-35A Completes First Flight
The Lockheed Martin X-35A, the demonstrator for the Joint Strike Fighter program, completed its first flight. It was later converted into the X-35B for STOVL testing.
First F-35B Rolled Off Production Line
The first weight-optimized F-35B, the Short Take-Off and Vertical Landing (STOVL) variant, was rolled off the line at Lockheed Martin's Fort Worth facility after significant weight-reduction efforts.
F-35B Achieves First Vertical Landing
The F-35B successfully performed its first vertical landing at Naval Air Station Patuxent River, Maryland, a crucial milestone for its STOVL capabilities.
US Marine Corps Declares F-35B Initial Operational Capability (IOC)
The U.S. Marine Corps declared IOC for the F-35B with Marine Fighter Attack Squadron 121 (VMFA-121) in Yuma, Arizona, becoming the first F-35 variant to achieve operational status.
USMC F-35B Squadron Deploys with UK Carrier Strike Group 21
Marine Fighter Attack Squadron 211 (VMFA-211) deployed aboard HMS Queen Elizabeth as part of the UK Carrier Strike Group 21, marking a significant international integration of the F-35B.
F-35B Conducts Sea Trials on Japan's JS Kaga
A U.S. F-35B Lightning II conducted groundbreaking sea trials aboard Japan's JS Kaga in the Eastern Pacific, demonstrating the successful integration of advanced fighter technology with the Izumo-class destroyer.
Japan Deploys First F-35B Jets to Nyutabaru Air Base
The Japan Air Self-Defense Force (JASDF) deployed F-35B stealth fighter jets to Nyutabaru Air Base, marking Japan's first operational deployment of the variant, enhancing its defense capabilities in the East China Sea.
Pentagon Reduces F-35 Orders for FY2026
The Pentagon significantly reduced planned procurements of F-35 fighters for Fiscal Year 2026, cutting orders for the F-35B to 11 aircraft, citing low availability, software issues, and funding shortages.
UK Completes First Tranche of F-35B Deliveries
The UK Ministry of Defence confirmed receipt of the last of its initial 48 contracted F-35B Lightning IIs, with 47 aircraft operational after one loss.
First Operational F-35Bs Begin TR-3 Upgrade Work at FRCE
Fleet Readiness Center East (FRCE) began converting the first operational F-35B Lightning II aircraft from Technology Refresh 2 (TR-2) to the advanced Technology Refresh 3 (TR-3) configuration, a major step towards Block 4 upgrades.
UK and Italy Expand F-35 Combat Power with Block 4 Sovereign Weapons Integration
Lockheed Martin secured a $74.2 million contract modification to integrate sovereign weapons under the Block 4 modernization program for the UK and Italian F-35 fleets, enhancing operational flexibility.
Report: Some USMC F-35Bs Flying Without Radar Due to Delays
Reports indicated that six U.S. Marine Corps F-35Bs were flying with ballast instead of their radar due to delays in the new AN/APG-85 radar, highlighting ongoing challenges with Block 4 upgrades.
US Marine Corps F-35B Crashes in California
A U.S. Marine Corps F-35B stealth fighter plane crashed near Marine Corps Air Station Miramar in San Diego, California. The pilot ejected safely and was transported to a medical facility with non-life-threatening injuries.
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🔍Deep Dive Analysis
The F-35B Lightning II, a critical component of the Joint Strike Fighter program, was developed to provide a 5th-generation, stealth-capable, multirole fighter with Short Take-Off and Vertical Landing (STOVL) capabilities. This unique design allows it to operate from amphibious assault ships and austere forward bases, offering unparalleled operational flexibility for forces like the U.S. Marine Corps and the UK Royal Navy. The U.S. Marine Corps declared Initial Operational Capability (IOC) for the F-35B on July 31, 2015, with a squadron of 10 F-35Bs ready for worldwide deployment.
Throughout its development, the F-35B program has faced significant challenges, including cost overruns, software delays, and technical issues. Early production models, for instance, were found to have structural defects that could limit their service life by 2026, though planned design changes aim to address this. The total program cost over its lifetime is estimated to exceed $1.7 trillion, making it one of the most expensive military programs in history. Despite these hurdles, the F-35B has seen increasing global adoption, with Italy, Japan, and the United Kingdom operating the variant.
A key turning point in recent years has been the ongoing Technology Refresh 3 (TR-3) and Block 4 modernization efforts. TR-3, which serves as the backbone for Block 4, introduces a major increase in computing power, memory, and processing capacity, along with hardware for advanced electronic warfare and future mission systems. Deliveries of F-35s with TR-3 upgrades resumed in July 2024 after a year-long pause, though initial testing of the upgraded Engine Core Upgrade (ECU) is expected by 2026, with deliveries projected to begin in 2029. The Block 4 program itself promises over 75 major updates, including increased payload capacity and integration of new weapons like the AIM-260 JATM and SPEAR 3 missile.
As of 2026, the F-35B continues to be actively deployed and upgraded. In June 2026, the Fleet Readiness Center East delivered its first F-35Bs with TR-3 upgrades, marking a significant step in modernizing the fleet. The UK and Italy secured a contract modification in June 2026 to integrate sovereign weapons under the Block 4 program, enhancing their F-35 fleets' combat capabilities. However, challenges persist; in June 2026, it was reported that some U.S. Marine Corps F-35Bs were flying with ballast instead of their radar due to delays in the new AN/APG-85 radar, highlighting ongoing issues with Block 4 implementation. The U.S. Marine Corps' 2026 aviation plan outlines that it will operate 205 F-35Bs and 56 F-35Cs by the end of 2026, cementing the F-35 as its sole tactical fighter.
Recent operational events include Japan's deployment of F-35B stealth fighters to Nyutabaru Air Base in August 2025, a move that was delayed from 2024. The UK confirmed in March 2026 that it had received the last of its first 48 contracted F-35B Lightning IIs, with 47 operational after one loss. In a notable incident, a U.S. Marine Corps F-35B crashed near Marine Corps Air Station Miramar in San Diego, California, on July 31, 2026, though the pilot ejected safely. The Pentagon also reduced its planned F-35 procurements for Fiscal Year 2026, cutting orders for the F-35B to 11 aircraft, amidst concerns over availability, software issues, and funding shortages. Despite these setbacks, Lockheed Martin delivered a record 191 F-35s across all variants in 2025, clearing a backlog caused by TR-3 issues and demonstrating continued global demand.
What If...?
Explore alternate histories. What if F-35B Lightning II made different choices?