A F-35 Lightning II conducts the first weapons separation test of an BLU-137/B Bunker Buster Bomb. These bombs are used extensively in Syria against terrorist hideouts and supply depots

The US Air Force has awarded multiple contracts worth over $896 million to two US-based firms for production of 2000-pound class bunker buster bombs, built around an improved warhead called the BLU-137/B, the Department of defence announced Wednesday.

The contracts worth $476 million and $419 million were awarded to Ohio-based Superior Forge and Steel Corp. and Chicago-based Finkl & Sons Co., respectively, for BLU-137/B penetrator warhead production.

Each firm are contracted to produce “BLU-137/B penetrator warhead bodies with a guaranteed production of 300 bodies during the first year with a possibility of up to 3,500 bodies in the subsequent four years”, the statement says.

Work will be performed in Lima, Cincinnati and Falconer, Chicago, Corry, Pennsylvania; and Burr Ridge, Illinois, and is expected to be completed by May 3, 2020.

The BLU-137/B is intended to provide improvements in capability and survivability over the BLU-109/B and BLU-109C/B. The BLU-109/B has a steel casing about 1 inch (25.4 mm) thick, filled with 530 lb (240 kg) of Tritonal. It has a delayed-action tail-fuse. The BLU-109 entered service in 1985. This weapon can penetrate 4–6 feet of reinforced concrete, which is greater than the 3 foot capability of the Small Diameter Bomb.