US Air Force receives first SiAW air-to-ground missile to strike mobile targets in hostile environments.

On November 18, 2024, Northrop Grumman announced the delivery of the first Stand-in Attack Weapon (SiAW) air-to-surface missile to the U.S. Air Force. The delivered missile, an inert test version, will be used to verify that the launch aircraft can safely carry and release the weapon. This marks the beginning of the flight testing phase, a critical step in the missile's development aimed at addressing modern Anti-Access/Area Denial (A2/AD) challenges, especially against mobile targets.
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Northrop Grumman's SiAW air-to-ground missile incorporates lessons learned from the AGM-88G Advanced Anti-Radiation Guided Missile-Extended Range (AARGM-ER), which has been under development with the US Navy. (Picture source: Northrop Grumman)

In September 2023, the U.S. Air Force awarded Northrop Grumman a contract worth approximately $705 million for the development and testing of the Stand-in Attack Weapon (SiAW). The contract includes completing a flight test program and achieving initial operational capability by 2026. The Air Force plans to acquire up to 3,000 SiAW missiles, starting with 400 units by 2028. The SiAW program follows a phased development approach: Phase 2.1 will conclude with a guided vehicle flight test, while Phase 2.2 involves three additional flight tests and the delivery of prototype missiles and test assets. Following successful tests, the U.S. Air Force plans to field the SiAW as part of its broader strategy to address Anti-Access/Area Denial (A2/AD) challenges and enhance strike capabilities against time-sensitive targets.

The SiAW is a tactical air-to-ground missile designed to strike rapidly relocatable targets. These include theater ballistic missile launchers, cruise and anti-ship missile launchers, electronic warfare systems, GPS jamming platforms, anti-satellite systems, and integrated air defense nodes. The weapon is intended for deployment with the U.S. Air Force’s fifth-generation aircraft, such as the F-35A Lightning II, where it can be carried in internal weapon bays. It may also be integrated with other platforms, including the B-21 Raider stealth bomber, as well as unspecified future advanced aircraft.

The SiAW design incorporates open systems architecture to enable rapid subsystem upgrades, addressing evolving threats. The missile is also designed with tail control for enhanced maneuverability and survivability. Its propulsion system is expected to meet operational range requirements. Northrop Grumman has emphasized its use of digital engineering to support the missile’s design and development, aligning with the U.S. Air Force’s focus on agile acquisition processes.

Northrop Grumman's SiAW builds on its own expertise, incorporating lessons learned from the AGM-88G Advanced Anti-Radiation Guided Missile-Extended Range (AARGM-ER), which has been under development with the US Navy. While similar externally, SiAW incorporates distinct features to address a wider range of targets. The AARGM-ER itself includes components such as a GPS-assisted inertial navigation system, millimeter-wave radar for non-emitting target detection, and a datalink system that can use off-board targeting data. SiAW adapts these features and incorporates an improved warhead and fuze for broader target capabilities.

Northrop Grumman’s work on the Stand-in Attack Weapon (SiAW) is part of a broader effort to modernize U.S. air-to-ground strike capabilities. The missile program originated in 2022, when the U.S. Air Force awarded initial development contracts to multiple companies, including Northrop Grumman, Lockheed Martin, and L3Harris Technologies. Northrop Grumman was subsequently selected as the prime contractor in September 2023. The program supports the Air Force’s Middle Tier Acquisition strategy, emphasizing rapid development and prototyping.

The U.S. Air Force’s Fiscal Year 2025 budget outlines plans to integrate the SiAW into its arsenal alongside interim capabilities provided by the AARGM-ER. This includes the procurement of 128 AARGM-ER missiles in 2025, following earlier acquisitions in 2023 and 2024. By combining these systems, the Air Force aims to enhance its ability to strike high-value targets in contested environments. The SiAW program’s relevance extends beyond the U.S. Air Force. Potential applications include surface-to-surface variants, such as the Advanced Reactive Strike (ARES) missile concept, which could be launched from ground-based or shipborne platforms. Allied nations, some of which are already acquiring AARGM-ER systems, may also express interest in the Stand-in Attack Weapon (SiAW) for similar mission profiles.