US Air Force Wants to Purchase New GBU-57 MOP Bunker-Penetrating Bombs

The U.S. Air Force plans to purchase additional GBU-57 Massive Ordnance Penetrator (MOP) bunker-busting bombs to replenish stockpiles after Operation Midnight Hammer in Iran.

This was reported by The Aviationist, citing U.S. Air Force documents.

The documents state that the purchase is “critically needed to replenish the GBU-57 stockpiles expended during the operation in Iran.” Fourteen such bombs were dropped during the operation.

The contract provides for the supply of both complete munitions in the MOP All-Up-Round (AUR) configuration and individual tail kits. The estimated start date for tail kit deliveries is January 10, 2028.

Details of the procurement remain limited, and the description of the required supplies in the documents is partially redacted. The total value of the purchase is listed at more than $100 million, but specific data on the exact amount, number of munitions and delivery schedule are classified.

The documents emphasize that the purchase is necessary to restore the combat readiness of the unit, the name of which has been redacted.
They also state that replenishing stockpiles will ensure the ability of U.S. Air Force Global Strike Command (AFGSC) to support strategic contingency plans for all combatant commands (COCOMs).

The U.S. military had previously signaled its intention to procure new munitions in a budget reprogramming request submitted in August 2025.

In that document, the Air Force outlined the need for funding to replace several types of weapons used during Operation Midnight Hammer, including GBU-39 Small Diameter Bombs, AGR-20F Falco guided missiles and GBU-57 MOPs. The total funding request amounted to $123 million.

GBU-57 Massive Ordnance Penetrator

The GBU-57 Massive Ordnance Penetrator (MOP) is a U.S.-made precision-guided, large-caliber bunker-busting bomb designed to destroy deeply buried and heavily fortified targets, including underground command posts and weapons storage facilities.

The bomb weighs about 13.6 metric tons, making it one of the heaviest conventional bombs in the world.

Its casing is made of high-strength steel designed to withstand extreme stress when penetrating soil or reinforced concrete.

The GBU-57 is equipped with a GPS guidance system integrated with inertial navigation, providing high accuracy. After release, the bomb penetrates soil or structural layers before detonating with a delay inside the target.

The only operational carrier of the GBU-57 is the B-2 Spirit strategic bomber, which carries the weapon in its internal bays. The B-21 Raider is expected to be integrated as a carrier in the future.