WASHINGTON — The Air Force awarded Northrop Grumman a $705 million contract to develop and test a high-speed air-to-ground weapon known as a stand-in attack weapon that the F-35 Joint Strike Fighter could wield to destroy enemy targets.

Northrop said Monday that its work on the second phase of the weapon, which is also referred to as SiAW, will take place over the next 36 months in Northridge, California, and the company’s missile integration facility at Allegany Ballistics Laboratory in West Virginia.

The work will include further development of the weapon, platform integration, and completing a flight test program so the SiAW can be rapidly prototyped and quickly sent to the field, the company said. A guided vehicle flight test will wrap up the first part of this second phase, and the second part will conclude with three more flight tests and the delivery prototype missiles and test assets.

The Air Force wants this weapon to reach initial operational capability by 2026.

Northrop was one of three companies, including Lockheed Martin and L3Harris, that in May 2022 each received $2 million contracts from the Air Force for the first phase of developing the SiAW.

The Air Force wants this weapon to strike enemy air defense targets on the ground that could be rapidly moved, such as integrated air defense systems, ballistic missile launchers, land-attack and anti-ship cruise missile launchers, GPS jammers, and anti-satellite systems.

A stand-in weapon has a shorter range than standoff weapons, so an F-35 would likely fire the SiAW close to the target after penetrating enemy airspace. A standoff weapon is meant to be fired from further away, beyond the reach of enemy defenses.

The Air Force in recent years has sought to update its aircraft and arsenals to be able to fight in a contested environment against an advanced enemy such as China, and away from the two decades of war in the Middle East which largely took place in uncontested airspace. The service’s work to develop a missile targeting enemy air defenses is another sign of that shift.

Northrop said it will build the SiAW using open architecture, which will allow its subsystems to be quickly upgraded with new capabilities.

A Northrop official told Defense News in June 2022 that the F-35 would have to carry the SiAW within its internal weapons bay to avoid compromising the jet’s stealth capabilities. This would rule out carrying the weapon on an external mount, he said. And he said it is unlikely that the F-22, which has a smaller internal bay, would have enough room to carry the SiAW.

The SiAW program is heavily focused on digital engineering and design, and is the first time the Air Force has had a fully 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,” Susan Bruce, Northrop’s vice president for advanced weapons, said in the company’s statement.

Northrop said last year that it planned to use its experience from creating the Advanced Anti-Radiation Guided Missile-Extended Range, or AARGM-ER, for the Navy and integrating it onto the F-35 as it develops the SiAW.