The AAM-4B is Japan's improved Type 99 medium-range air-to-air missile for F-2 and F-15 fighters. JASDF test-history material identifies the AAM-4 improved test article as the current AAM-4B, while MOD budget papers keep funding it as fighter ammunition and CSIS notes its AESA seeker.
AAM-4B is the current designation of the improved AAM-4/Type 99 medium-range air-to-air missile family member.
| Variant | Configuration | Designation notes |
|---|---|---|
| AAM-4 | Baseline Type 99 medium-range air-to-air missile | JASDF test-history material lists XAAM-4, now 99式空対空誘導弾 AAM-4, practical testing in 1998-1999; the later AAM-4 improved model is identified as the current AAM-4B. Sources: JASDF Guided Weapons Tests 1967-1999, JASDF Guided Weapons Tests 2001-2017 |
Official Japanese material identifies the fighters that carry this missile.
| Carrier | Carrier type | Carriage evidence |
|---|---|---|
 | Fighter aircraft | Japan's Ministry of Defense lists AAM-4B procurement for F-2 aircraft, and CSIS notes the missile was already in service with the F-2 fleet. Sources: JASDF Overview 2024, Defense Programs and Budget of Japan 2023, Progress and Budget in Fundamental Reinforcement of Defense Capabilities 2024, CSIS Missile Threat: Japan Mulls Equipping F-15J with Domestically-Produced Air-to-Air Missile |
 | Fighter aircraft | The Ministry of Defense continues to fund AAM-4B for F-15 aircraft, and CSIS reported a July 2019 request to integrate the missile on the F-15J fleet. Sources: JASDF Overview 2024, Defense Programs and Budget of Japan 2023, Progress and Budget in Fundamental Reinforcement of Defense Capabilities 2024, CSIS Missile Threat: Japan Mulls Equipping F-15J with Domestically-Produced Air-to-Air Missile |
JASDF test-history material lists practical testing for the new medium-range air-to-air missile XAAM-4, now the Type 99 AAM/AAM-4, from April 1998 to March 1999.
Sources: JASDF Guided Weapons Tests 1967-1999
JASDF test-history material identifies 99式空対空誘導弾（改）, AAM-4（改）, as the current AAM-4B and lists practical testing from October 2007 to March 2009.
Sources: JASDF Guided Weapons Tests 2001-2017
The Ministry of Defense budget request lists AAM-4B as aircraft ammunition purchased in bulk over three years, showing the missile entering a recurring procurement pipeline.
Sources: FY2015 Budget Request
CSIS reported that Japan's Ministry of Defense issued a request for proposals to integrate AAM-4B on the F-15J fleet, extending the missile beyond the F-2.
Sources: CSIS Missile Threat: Japan Mulls Equipping F-15J with Domestically-Produced Air-to-Air Missile
The FY2024 defense buildup budget continues AAM-4B procurement at JPY 16.3 billion for F-2 and F-15 aircraft.
Sources: Progress and Budget in Fundamental Reinforcement of Defense Capabilities 2024
The FY2026 defense buildup budget lists JPY 7.3 billion for AAM-4B under securing ammunition, showing the missile remained a current procurement line.
Sources: Progress and Budget in Fundamental Reinforcement of Defense Capabilities 2026
These are budget lines rather than public per-missile unit prices. They show how AAM-4B procurement has remained a recurring fighter armament item.
| Budget year | Amount | What the line says | Source |
|---|---|---|---|
| FY2015 request | JPY 19.0 billion | Bulk purchase of aircraft ammunition for three years, with expected savings of JPY 2.6 billion. | FY2015 Budget Request |
| FY2023 budget | JPY 11.9 billion | AAM-4B procurement for F-2 and F-15 aircraft. | Defense Programs and Budget of Japan 2023 |
| FY2024 budget | JPY 16.3 billion | AAM-4B procurement for F-2 and F-15 aircraft. | Progress and Budget in Fundamental Reinforcement of Defense Capabilities 2024 |
| FY2025 budget | JPY 13.9 billion | AAM-4B procurement under the securing-ammunitions budget. | Progress and Budget in Fundamental Reinforcement of Defense Capabilities 2025 |
| FY2026 budget | JPY 7.3 billion | AAM-4B procurement under the securing-ammunitions budget. | Progress and Budget in Fundamental Reinforcement of Defense Capabilities 2026 |
