The Vympel R-37 (NATO reporting name: AA-13 "Axehead")^[1] is a Russian hypersonic air-to-air missile with very long range. The missile and its variants also had the names K-37, izdeliye 610 and RVV-BD (Ракета Воздух-Воздух Большой Дальности (Raketa Vozduh-Vozduh Bolshoy Dalnosti), "Long range air-to-air rocket"), and the NATO codenames "Axehead" and "Andi".^[2] It was developed from the R-33.

It is designed to shoot down tankers, AWACS and other C4ISTAR aircraft^[1] while keeping the launch platform out of range of any fighters that might be protecting the target.

According to Janes there are two variants, the R-37 and the R-37M; the latter conceived as having a jettisonable rocket booster that increases the range to "300–400 km" (160–220 nm).^[2] In 2023, Rosoboronexport introduced the export version of the R-37M, designated RVV-BD. It has a launch range of up to 200 kilometres (120 mi; 110 nmi) and maximum altitude of 25 kilometres (82,000 ft) with a 60 kilograms (130 lb) warhead. The missile is compatible with Sukhoi Su-57, Sukhoi Su-35, Mikoyan MiG-31BM and Mikoyan MiG-35.^[3][4]

The R-37 was developed from the R-33. For compatibility with aircraft that did not have the MiG-31's sophisticated radar, the semi-active seeker was replaced with a variant of the Agat 9B-1388 active seeker.^[1] Similarly, folding tail controls allow semi-conformal carriage^[1] on planes that are not as big as the MiG-31.

Mid-body strakes enhance lift^[1] and hence increase range. According to Defence Today, the range depends on the flight profile, from 80 nautical miles (150 km) for a direct shot^[1] to 215 nautical miles (398 km) for a cruise glide profile.^[1]

The R-37M designation has since been used for a modernized variant of the missile, also known as RVV-BD (Raketa Vozduh-Vozduh Bolyshoy Dalnosty, or Long-Range Air-to-Air Missile). R-37M's range exceeds 200 km, and it is capable of hypersonic speeds (~Mach 5).^[5] It will be carried by the modernized MiG-31BM interceptors and Su-35S and Su-57 multirole fighters.^[6]

A further derivative designed for internal carriage in the Su-57, designated as Izdeliye 810, has folding rear fins, shorter strakes, and updated seeker and motor.^[7]

The missile can attack targets at altitudes of 15–25 kilometres (49,000–82,000 ft), guided semi-actively or actively through the Agat 9B-1388 system.^[8]

The missile was designed in the early 1980s and first flown in 1989.^[2] Testing of the R-37 continued through the 1990s,^[2] and in 1994, a trial round scored a kill at a range of 162 nautical miles (300 km).^[1] However, the program appears to have been dropped around 1998 on grounds of cost.^[2]

Work on the missile appears to have restarted in late 2006,^[2] as part of the MiG-31BM program to update the Foxhound with a new radar and ground attack capability.^[2]

In 2018, the R-37M had finished its operational validation tests.^[9][10]

On October 19, 2022, Russian, and subsequently Indian media claimed that the Su-57 stealth fighter shot down a Ukrainian Su-27 using the R-37M missile.^{[11][unreliable source?][12]}

Zvezda TV reports have recorded the Su-35 carrying the R-37, apparently as part of an air combat loadout. In this configuration, the craft carries two R-73s in the central wing pylon, two R-77s slung underneath the engine nacelles, and two R-37s on the hardpoints between the engines, with an option to carry a few more missiles, such as a Kh-31 anti-radiation missile.

• AIM-54 Phoenix – (United States of America)
• AIM-152 AAAM – (United States of America)
• AIM-260 JATM – (United States of America)
• Novator KS-172 – (Russia)
• PL-21 – (People's Republic of China)
• Long-Range Engagement Weapon – (United States of America)
• Meteor – (multinational corporation)
• Astra Mark 3 – (India)