Indian Air Force personnel were reportedly prevented from approaching US Air Force F-35 stealth fighters during the multinational Tarang Shakti-2026 exercise, a move that has reignited discussion over whether India’s acquisition of the Russian-made S-400 Triumf air-defence system is complicating prospects for closer cooperation on fifth-generation combat aircraft, The Week reported.

The issue gained attention after Air Chief Marshal AP Singh revealed that Indian personnel were not permitted to go near the American fighters that participated in the exercise. Responding to speculation surrounding reports of a possible F-35 sale to India, Singh remarked that American personnel would not even allow Indian counterparts near the aircraft, making talk of a sale appear premature.

He also clarified that the United States has not made any official offer to sell F-35 fighters to India.

The comments raised questions about why such strict restrictions were imposed during a major international exercise involving air forces from multiple nations. Although no official explanation has been provided by either side, defence observers and several media reports have pointed to India’s continued induction of the Russian S-400 air-defence system as a possible factor.

The United States has long maintained that operating F-35 stealth fighters alongside the S-400 creates significant security concerns.

Washington argues that the advanced radar network associated with the Russian system could collect valuable data on the aircraft’s radar signature, flight characteristics and stealth performance.

Those concerns were central to the dispute between the United States and Turkey. After Ankara acquired the S-400, it was removed from the F-35 program despite being a long-standing participant and industrial partner in the project. American officials argued that the simultaneous operation of the two systems could expose sensitive information that might ultimately benefit Russia.

Former US European Command chief General Tod Wolters publicly stated that the F-35 should not operate in the vicinity of the S-400. He warned that the Russian system would seek to exploit and analyse the aircraft’s capabilities, adding that Washington had no interest in allowing Russia to gain insight into the F-35 from either a radar or operational perspective.

Defence specialists have similarly warned that repeated tracking of the aircraft by advanced S-400 radars could allow analysts to build a detailed picture of its stealth profile under different flight conditions.

The concern extends beyond simple detection, focusing instead on the gradual collection of electronic and radar data that could reveal potential vulnerabilities.

Former US Secretary of State Mike Pompeo also opposed operating the two systems together, arguing that the F-35 could not safely operate in an environment where the S-400 remained significantly active.

American and NATO officials have consistently maintained that the primary risk lies in the potential accumulation of intelligence regarding the aircraft’s low-observable characteristics.

Such information could theoretically help adversaries refine detection methods and counter-stealth tactics against F-35 fleets operated by the United States and its allies.

India, meanwhile, continues to field the S-400 as a critical component of its layered air-defence architecture. The system is regarded as one of the most capable long-range surface-to-air missile platforms in service and plays a central role in India's air-defence strategy.

While there is no evidence that the restrictions imposed during Tarang Shakti-2026 were directly linked to India's S-400 deployment, the episode reflects Washington’s long-standing sensitivity regarding the protection of F-35 technology.

The incident also highlights the challenges that can arise when countries seek to operate advanced Western and Russian military systems within the same defence ecosystem.

As debates over India's future fighter requirements continue, the F-35 remains a highly protected platform whose stealth technologies are treated as among the most closely guarded capabilities in the US military inventory.

The restrictions observed during the exercise underscore the extent to which those safeguards continue to influence operational interactions with partner nations.

Agencies