Belgium to Arm F-35A Fleet with AIM-9X Sidewinder Missiles in $66 Million U.S. Deal

Belgium is set to enhance the air-to-air capabilities of its future F-35A Lightning II fleet through the acquisition of AIM-9X Block II Sidewinder missiles from the United States. The U.S. State Department has approved a Foreign Military Sale (FMS) valued at approximately $66 million, marking a key milestone in Belgium’s modernization of its air combat forces within NATO.

Deal Overview and Missile Package Details

On September 25, 2025, the U.S. Defense Security Cooperation Agency (DSCA) formally notified Congress of Belgium’s request to purchase 120 AIM-9X Block II tactical missiles along with associated equipment and services. The approved package includes:

• 120x AIM-9X Block II tactical missiles
• 12x CATM (Captive Air Training Missiles) for training purposes
• 8x Guidance Units (spares or conversions)
• Missile containers and support equipment
• Technical documentation and logistics support

The prime contractor for the deal is Raytheon Missiles & Defense, headquartered in Tucson, Arizona.

AIM-9X Block II: Capabilities and Compatibility with F-35A

The AIM-9X Block II is the latest evolution of the venerable Sidewinder family of short-range infrared-guided air-to-air missiles. Key enhancements over earlier variants include:

• Lock-on-after-launch (LOAL) capability for internal carriage in stealth fighters like the F-35
• Datalink connectivity enabling mid-course updates via aircraft systems
• An improved guidance unit with enhanced counter-countermeasures resistance
• A highly agile thrust-vectoring control system for high off-boresight engagements

This missile complements the F-35’s sensor fusion suite by allowing pilots to engage targets detected by onboard or offboard sensors without requiring visual contact or direct radar lock prior to launch. The LOAL feature is particularly critical for stealth aircraft that carry weapons internally to preserve low observability.

Strategic Context: Belgium’s Transition from F-16 to F-35A

Belgium selected the Lockheed Martin F-35A Lightning II in October 2018 as a replacement for its aging fleet of around 54 F-16AM/BM Fighting Falcons under its Air Combat Capability Program (ACCaP). The country plans to acquire up to 34 fifth-generation fighters, with initial deliveries expected by late 2025 or early 2026.

The integration of advanced munitions like the AIM-9X aligns with Belgium’s broader objective of maintaining full interoperability within NATO’s fifth-generation fighter ecosystem. Other European operators of both the F-35 and AIM-9X include Norway, Denmark, Italy, Poland, Finland and The Netherlands—many of whom are also transitioning from legacy platforms like the F/A‑18 Hornet or Eurofighter Typhoon.

NATO Interoperability and Regional Deterrence Implications

The addition of AIM‑9X missiles enhances Belgium’s ability to contribute meaningfully to NATO’s integrated air defense posture and quick reaction alert missions across Europe. As tensions persist on NATO’s eastern flank—particularly due to Russia’s ongoing war against Ukraine—the modernization of allied air forces remains a strategic priority.

The missile’s compatibility with helmet-mounted cueing systems such as JHMCS-II further improves pilot situational awareness and engagement timelines during close-range dogfights or defensive counter-air scenarios—capabilities increasingly relevant given evolving Russian aerial tactics including drone swarms and standoff jamming platforms.

Industrial Participation and Logistics Considerations

No offset agreements were disclosed as part of this particular missile sale; however, Belgium has previously negotiated industrial participation packages related to its overall F‑35 procurement via Lockheed Martin’s global supply chain initiatives. Raytheon may provide sustainment training and technical assistance through existing NATO logistics frameworks such as NAMSA (NATO Support and Procurement Agency).

The inclusion of CATMs ensures Belgian pilots can train realistically without expending live munitions—a cost-effective measure critical during force transition phases from legacy platforms like the MLU-upgraded F‑16AM/BM fleet.

Outlook: Future Munitions Integration for Belgian Air Force

This deal likely represents only one component in a broader munitions roadmap for Belgium’s future fighter force structure. Additional procurements may include:

• AIM‑120D AMRAAMs for beyond visual range engagements (already integrated on Belgian legacy jets)
• Joint Direct Attack Munition (JDAM) kits or GBU‑53/B StormBreaker smart bombs for precision strike missions
• SPEAR family weapons or other stand-off glide munitions pending European collaborative programs

The successful integration of these systems will be key not only for national defense but also for coalition operations under EU/NATO frameworks such as Baltic Air Policing or Operation Inherent Resolve rotations.

Conclusion

The approved sale of AIM‑9X Block II missiles marks an important step in aligning Belgium’s next-generation fighter capabilities with those of other advanced NATO air forces. As deliveries begin over the coming years alongside new-build F‑35As, Belgian pilots will gain access to one of the most capable short-range air-to-air weapons currently fielded—a significant leap from legacy Sidewinders carried on their current Viper fleet.