Delivery of Ultra-Long Range 40N6 Missiles For India’s S-400 Air Defence Systems Confirmed: How Capable Are They?

Indian Air Force Air Chief Marshal Amar Preet Singh has confirmed that the service’s newly procured S-400 long range air defence systems are able to engage enemy aircraft over extreme distances, and demonstrated this capability during clashes with Pakistani forces in early May. The S-400 shot down “one large aircraft, which could be an ELINT aircraft or an AEW&C aircraft, which was taken out from a distance of about 300km,” he observed, noting that this was “the largest-ever recorded surface-to-air kill that we can talk about.” Although the S-400 first entered service in the Russian Aerospace Forces in 2007 equipped with 48N6E3 surface-to-air missiles, which provided a 250 kilometre engagement range, the system’s maximum engagement range was extended to 400 kilometres in the late 2010s due to the integration of the 40N6. The unique missile class provides capabilities that no non-Russian system is known to have. The reported 300 kilometre range kill makes it almost certain that India has been delivered the 40N6.

The development of the 40N6 faced significantly delays, and while its service entry in both China and Russia in the late 2010s was confirmed, it remained unknown whether the missiles has been sold to the S-400’s other operators including Belarus, Algeria and Turkey. The missile’s deployment by the Indian Air Force significantly constrains Pakistan’s strategic depth, and allows for the targeting of aircraft at all altitudes deep into hostile territory by the six S-400 battalions intended to be deployed near Pakistani territory. The 40N6 achieves a very long targeting range over the earth’s curvature by using targeting data either from forward deployed ground based radars, or from airborne radars such as those on Indian Air Force Su-30MKI fighters. The missile’s two part trajectory first sees it ascend to altitudes above the Armstrong Limit at close to 30,000 meters, before descending using this targeting data to strike aircraft at altitudes between 30,000 metres and 5 meters off the ground.

The 40N6 is well suited to being utilised alongside India’s A-50 airborne early warning and control (AEW&C) systems and Su-30MKI fighters due to the particularly large and powerful airborne radars they deploy, which allow them to ‘peer’ far into Pakistani airspace to guide the missiles to their targets. With the Indian Defence Ministry currently considering procuring Russian Su-57 fifth generation fighters, which combine more advanced sensors with stealth capabilities, these could seriously further increase the utility of 40N6 missiles in the Indian arsenal. The Russian Aerospace Forces have used 40N6 missiles to target Ukrainain aircraft, and are confirmed to have paired them with A-50 AEW&Cs to increase their utility. Reports of the missiles’ use in the Ukrainian theatre began to surface in late 2023, with assessments of the shootdown of a Ukrainain F-16 in April 2025 indicating that had been achieved using the missiles.

The S-400’s service entry has been significantly more revolutionary for Indian air defence capabilities than it has for other foreign clients, due to both the much larger numbers that have been ordered, and due to the fact that the country’s surface-to-air missile capabilities were previously very limited. A $5.43 billion contract for ten battalions’ worth of S-400s was signed in October 2018, making India by far its largest foreign client, with Delhi proceeding with the deal despite tremendous Western pressure and threats of American economic sanctions. The Indian government harshly condemned Western efforts at coercion over the issue, slamming threats of sanctions as illegitimate and illegal, and was widely seen by analysts to have effectively called Washington’s bluff over such threats since the promised sanctions were never imposed.

The first regiment’s worth of S-400s delivered to India was deployed near its western border with Pakistan in December 2021, with a second regiment’s worth delivered the following year stationed near the northern border with China. It remains uncertain whether 40N6 missiles were delivered from 2021, or at a later date. Unconfirmed reports of Indian interest in the Russian S-500 long range air defence system could lead to further procurements of the 40N6 missile, which is used by both systems, although the S-500 also has access to longer ranged missiles with 600 kilometre engagement ranges.

The perceived importance of the S-400 for India’s air defence has grown both due to its reportedly outstanding performance against Pakistani air power during clashes in early May, and due to the severe underperformance of India’s Rafale fighter aircraft procured from France, which saw between one and four shot down reportedly by newly supplied Chinese J-10C fighters. With the competitiveness of European fighter aircraft having long been in serious question, India’s lack of significant recent procurements of high performance non-European fighters such as the F-18E/F offered by the United States, or the Su-57 offered by Russia, has left it heavily reliant on the S-400 to counterbalance the emerging superiority of Pakistan’s fighter fleet. The range of the 40N6 provides an effective means of engaging high value support aircraft at ranges over which non-Russian air defence systems would not be able to target them.