The F-35 is the initial platform for the Stand-in Attack Weapon (SiAW), and the USAF has indicated the B-21 bomber may also carry the weapon.
Northrop Grumman Corporation announced on Sep. 25, 2023 the US Air Force (USAF) has awarded the company an approximately $705 million contract to deliver the Stand-in Attack Weapon (SiAW), an air-to-ground weapon that accelerates the pivot to a new generation of air power.
- Northrop Grumman’s SiAW leverages the company’s weapons systems design, development and production expertise to deliver on the Air Force’s digital engineering priorities and accelerate capability for the warfighter.
- During the next 36 months, Northrop Grumman will further develop the weapon, conduct platform integration and complete the flight test program for rapid prototyping in preparation for rapid fielding. Work will be performed at the company’s Northridge, California facility and its factory of the future for missile integration at Allegany Ballistics Laboratory in West Virginia.

Susan Bruce, vice president, advanced weapons, Northrop Grumman, said in a company news release: “Northrop Grumman’s SiAW delivers on the Air Force’s desire for its first digital weapons acquisition and development program. With our expert digital engineering capabilities, this next-generation missile represents an adaptable, affordable way for the Department of Defense to buy and modernize weapons.”
SiAW is an air-to-ground weapon that will provide strike capability to defeat rapidly relocatable targets as part of an enemy’s anti-access/area denial environment. To adapt to ever-changing threats, the missile design features open architecture interfaces that will allow for rapid subsystem upgrades to field enhanced capabilities to the warfighter.
Phase 2 development is a continuation of the Air Force requirement for this first-of-its-kind Middle Tier Acquisition large weapon program focused on digital engineering, Weapon Open System Architecture and agility. The Air Force is targeting an initial operational capability by 2026. Phase 2 consists of two primary increments:
- Phase 2.1 concludes with a guided vehicle flight test.
- Phase 2.2 concludes with three additional flight tests and the delivery of SiAW leave-behind prototype missiles and test assets.

As reported by Air & Space Forces Magazine, the Air Force was looking toward a five-year development and production program that will provide SiAWs to operational units by 2026 under previous, classified competitive Phase 1 contracts to Northrop, L3Harris, and Lockheed Martin. The F-35 is the initial platform for the SiAW, and the USAF has indicated the B-21 bomber may also carry the weapon.
Northrop’s SiAW builds on its Advanced Anti-Radiation Guided Missile (AARGM), which in turn succeeds the AGM-88 HARM (High-speed Anti-Radiation Missile). The HARM, which entered service in the 1980s, was used with great effect during Operation Desert Storm by quickly homing in on and destroying ground-based search and track radars before they had a chance to move to a new location. The weapon was so effective that Iraqi radar operators were deterred from turning on their systems, knowing a HARM would likely arrive a few seconds later.
Photo credit: Northrop Grumman
