The Lockheed Martin F-35B Lightning II, a fifth-generation stealth fighter jet, is among the most advanced and expensive combat aircraft in the world, valued at over $110 million per unit. Designed for short take-off and vertical landing (STOVL), it represents a cornerstone of modern military aviation for NATO allies, including the United Kingdom. However, an incident in Kerala, India, where a British Royal Navy F-35B has been grounded since June 14, 2025, has spotlighted significant engineering, operational, and financial challenges facing the UK’s F-35 program.
The Kerala Incident: A Timeline of Events
On June 14, 2025, a British F-35B, part of the HMS Prince of Wales Carrier Strike Group, was conducting routine maritime exercises in the Indian Ocean, approximately 100 nautical miles off Kerala’s coast. Adverse weather conditions and reported low fuel levels forced the jet to make an emergency landing at Thiruvananthapuram International Airport. While the Indian Air Force (IAF) provided immediate logistical support, including refueling, a post-landing inspection revealed a critical hydraulic system failure, rendering the aircraft unflightworthy.
Initial repair attempts by a small team of Royal Navy technicians from the Prince of Wales were unsuccessful due to the complexity of the hydraulic issue, which affects critical systems like landing gear, brakes, and control surfaces. The jet, initially parked in the open at Bay 4 under Central Industrial Security Force (CISF) guard, endured Kerala’s monsoon rains for weeks, raising concerns about potential damage to its sensitive systems. The UK initially declined an offer from Air India to move the jet to a hangar, likely due to concerns over exposing its stealth and communication technologies.
By July 6, 2025, a 25-member team of British engineers, arriving via a Royal Air Force Airbus A400M with specialized equipment, moved the jet to the airport’s Maintenance, Repair, and Overhaul (MRO) facility to conduct repairs. Despite these efforts, reports suggested that the hydraulic failure might be beyond on-site repair, prompting plans to partially dismantle the jet and airlift it back to the UK using a C-17 Globemaster III. However, as of July 11, 2025, an Indian official indicated that repairs might succeed, potentially allowing the jet to fly back as early as the following week.
Engineering and Technology Gaps
The prolonged grounding of the F-35B in Kerala has exposed deeper systemic issues within the UK’s F-35 program, as highlighted by a recent National Audit Office (NAO) report. The report describes the program’s £11 billion expenditure as yielding a “disappointing return,” citing poor aircraft availability, engineering shortfalls, and delays in weapons integration.
Hydraulic System Failure
The hydraulic failure in the Kerala incident underscores reliability concerns with the F-35B. Hydraulic systems are critical for controlling flight surfaces and landing gear, and their failure can ground an aircraft indefinitely if not addressed with specialized expertise and parts. The inability of initial Royal Navy technicians to resolve the issue, followed by the need for a larger team with specialized equipment, suggests a lack of readily available technical resources within the UK’s operational framework.
Broader Reliability Issues
The NAO report points to three key reliability metrics for the F-35: Mean Flight Hours Between Critical Failures (MFHBCF), Mean Flight Hours Between Removal (MFHBR), and Mean Flight Hours Between Maintenance Events – Unscheduled (MFHBME-U). These metrics indicate persistent challenges in maintaining the F-35B’s mission readiness. The Kerala incident is not isolated; similar reliability issues have been reported globally, including a case in South Korea where an F-35 required extensive repairs after a belly landing, with costs nearly matching those of a new jet.
Program Delays and Capability Gaps
The UK’s plan to procure 138 F-35Bs has been hampered by delays, with only 38 delivered so far, pushing full operational capability to the end of 2025—two years behind schedule. The NAO highlights infrastructure gaps, personnel shortages, and delays in modernizing the fleet with Block 4 upgrades and Technical Refresh-3 software updates. These delays limit the jet’s ability to integrate new weapons systems and maintain technological superiority.
Financial and Operational Shortfalls
The NAO report estimates that expanding the UK’s F-35 fleet will cost over three times the initial budget, straining the Ministry of Defence’s (MoD) resources. The high maintenance costs and low availability rates further exacerbate the financial burden. For instance, the F-35’s sophisticated systems require certified Lockheed Martin engineers for certain repairs, as seen in the Kerala case, where dismantling and transport plans involve specialized teams to safeguard stealth technologies.
The operational impact is significant. The stranded jet has reduced the Prince of Wales Carrier Strike Group’s combat readiness during its Indo-Pacific deployment, part of Operation Highmast. The prolonged downtime has also sparked public relations challenges, with social media memes and Kerala Tourism’s humorous posts highlighting the jet’s extended stay. Dr. Sameer Patil, an analyst, noted that the longer the jet remains grounded, the more it damages the Royal Navy’s credibility and fuels disinformation.
Security and Diplomatic Implications
The F-35B’s sensitive technologies, including its stealth and sensor systems, have raised concerns about potential espionage while the jet sits on foreign soil. The UK’s initial reluctance to move the jet to a hangar reflects fears of exposing “protected technologies” to India or third parties. However, the strong defense ties between the UK and India, underscored by a bilateral treaty, have ensured robust security measures, with CISF personnel guarding the jet round-the-clock. The IAF’s coordination and logistical support further demonstrate the deepening UK-India military relationship.
The grounding of the British F-35B in Kerala is more than an isolated technical failure; it is a symptom of broader engineering, operational, and financial challenges facing the UK’s F-35 program. The hydraulic failure, coupled with the NAO’s findings of poor availability, delays, and cost overruns, highlights the complexities of maintaining a cutting-edge stealth fighter.
While the jet may soon return to the UK, either through repairs or airlift, the incident underscores the need for improved maintenance infrastructure, personnel training, and program management to ensure the F-35B’s reliability and operational readiness. As the UK navigates these challenges, its partnership with India has proven vital in managing this high-profile incident, reinforcing the importance of international cooperation in modern defense operations.