India to reach full airspace coverage as Russia completes final S-400 missile system deliveries.

As reported by the Hindustan Times on July 2, 2025, India is set to receive the final two regiments of the Russian-made S-400 Triumf surface-to-air missile system in 2026, completing the $5.5 billion deal signed in 2018. Three regiments have already been delivered between 2021 and 2023 and are operational in different regions of the country. Despite disruptions linked to Western sanctions on Russia’s defense-industrial base, Indian officials have confirmed that the deliveries are expected to follow the revised timetable. Once the remaining regiments are received, India will operate a total of five S-400 units, each with long-range engagement capability. The systems are expected to be deployed either to under-protected sectors or held as mobile reserves for flexible response planning.
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The full deployment of five S-400 regiments will significantly expand India’s capacity to detect and engage diverse aerial threats, including fighter aircraft, airborne early warning platforms, cruise missiles, and some types of ballistic missiles. (Picture source: RIA Novosti)

The S-400 procurement was approved by the Indian government in October 2018 during a bilateral meeting with Russian President Vladimir Putin in New Delhi, despite the threat of U.S. sanctions under the Countering America’s Adversaries Through Sanctions Act (CAATSA). India maintained its position of strategic autonomy in defense procurement, citing operational imperatives stemming from increasing threats along its western and northern borders, as well as long-standing cooperation with Russia. The first delivered regiment was deployed in Punjab, near the Pakistan border, in late 2021. A second regiment followed in 2022, reportedly fielded near the Chinese border. The third regiment entered service in 2023. The final two systems will allow the Indian Air Force to either fill remaining gaps in central or peninsular India or serve as flexible assets to respond to multi-front contingencies in contested or strategically important areas.

Each S-400 regiment supplied to India includes eight launchers, a command post, and a set of radar and support vehicles. The system can launch a combination of missiles designed for targets at different ranges and altitudes. The longest-range interceptor, the 40N6E, can engage airborne targets up to 400 kilometers away and is primarily intended to counter aircraft and airborne early warning platforms. The 48N6DM missile has a range of up to 250 kilometers and can intercept a variety of air-breathing threats. The 9M96E and 9M96E2 missiles are optimized for short to medium-range interception with ranges of approximately 40 to 120 kilometers, allowing the system to engage precision-guided munitions and tactical aircraft. The missiles are cold-launched vertically, allowing rapid engagement and reducing the system’s exposure to counter-battery fire. Their guidance systems use semi-active or active radar homing depending on the variant, with terminal speeds reaching several times the speed of sound.

The S-400’s radar suite includes the 91N6E Big Bird surveillance radar, which has a detection range of up to 570 kilometers against large targets, and the 92N6E Grave Stone engagement radar, which controls missile launches. These are supplemented by the 96L6 all-altitude radar and optional electronic support measures to detect low-flying or low-observable targets. Together, these radars allow one S-400 battery to simultaneously engage up to 36 targets with a total of 72 missiles in flight. The integration of the S-400 command and control structure into India’s existing air defense network allows it to function alongside other systems such as the Barak-8, Akash, Pechora, and OSA, creating a more comprehensive and overlapping defense structure. The S-400’s mobility allows India to reposition it as needed, which increases its utility across a wide operational spectrum, from strategic installations and urban centers to high-altitude contested zones.

The full deployment of five S-400 regiments will significantly expand India’s capacity to detect and engage diverse aerial threats, including fighter aircraft, airborne early warning platforms, cruise missiles, and some types of ballistic missiles. The ability to intercept threats beyond 250 kilometers allows the Indian Air Force (IAF) to deny airspace to adversaries far from the border, thereby increasing the reaction time for intercepts, reducing the vulnerability to saturation attacks, and allowing the IAF to cover a larger airspace with fewer units. This long-range capability reinforces the defense of strategic infrastructure, command centers, airbases, and urban areas. The system fills a gap in India’s current air defense posture that was previously limited by the reach of medium and short-range platforms.

India’s acquisition of the S-400 is part of a long-standing defense partnership with Russia, which supplied a wide range of military assets over several decades. Between 2000 and 2020, India imported more than $35 billion in military equipment from Russia, including Su-30MKI fighters, T-90S main battle tanks, Mi-17 helicopters, and various air defense systems. As of 2023, Russia remains India’s largest arms supplier, although its share has declined from nearly 70% in the early 2010s to just under 45% of Indian imports in recent years due to diversification toward Western and domestic suppliers. Today, Russia has adapted its defense relationship with India through local currency trade and non-dollar transactions, as well as co-production agreements to maintain the deliveries despite the sanctions imposed after 2022.

Once the fifth regiment is delivered in 2026, India will join the small group of countries with full operational S-400 capability, including Russia and China. The complete deployment will likely affect regional threat perceptions and aerial planning by Pakistan and China. In the west, the system's detection range allows monitoring of airspace well within Pakistani territory, potentially influencing flight operations and planning. In the east, the S-400 strengthens Indian airspace monitoring and missile interception capabilities in border areas such as Arunachal Pradesh and Ladakh. The system introduces complications for hostile aerial operations by reducing the probability of successful incursions or surveillance missions. Its completion is expected to reinforce India’s overall air defense strategy by integrating a credible long-range element into an already multi-layered system, thereby enhancing its capacity for independent deterrence and national defense planning across contested regions.