ARLINGTON— The U.S. Air Force (USAF) is moving to replenish GBU-57 Massive Ordnance Penetrator bombs used during 2025 strikes on Iranian nuclear facilities.
A new procurement deal aims to restore strategic readiness while the Pentagon prepares to transition to a next-generation bunker-busting weapon.
USAF Rebuilds Bunker-Buster Stock
The U.S. Air Force is finalizing a contract valued at more than $100 million with Boeing to replace GBU-57 Massive Ordnance Penetrator, or MOP, bombs expended during Operation Midnight Hammer in June 2025.
Partially redacted Air Force acquisition documents released in February confirm that the purchase is required to restore operational readiness following the weapons’ combat use. The bombs were employed against deeply buried nuclear facilities at Fordow and Natanz in Iran.
According to Air and Space Forces, the operation marked the first operational use of the 30,000-pound bunker-busting weapon.
The Air Force stated the acquisition ensures Air Force Global Strike Command maintains the strike capability needed for contingency plans across all combatant commands. The documents also justify limiting competition for the procurement due to the weapon’s specialized design and Boeing’s control of technical data.
Delivery of replacement tailkits for the bombs is projected to begin in January 2028, with full weapon assemblies also being procured. Exact quantities and final delivery timelines remain classified.
Operation Midnight Hammer Strike Overview
Operation Midnight Hammer involved 125 U.S. aircraft, including B-2 stealth bombers, F-35s, F-22s, F-16s, and aerial refueling tankers.
B-2 bombers delivered 14 MOP weapons during the operation. Six bombs struck the Fordow facility, and two hit Natanz. Additional strikes targeted Iran’s Isfahan facility using more than two dozen Tomahawk cruise missiles.
U.S. military officials stated the weapons performed as intended, penetrating underground structures before detonating. The bombs reportedly entered ventilation shafts at speeds exceeding 1,000 feet per second, generating blast and overpressure effects that damaged underground tunnels and equipment.
How the Massive Ordnance Penetrator Works
The GBU-57 MOP features a hardened steel casing designed to penetrate rock, reinforced concrete, and steel layers before detonation.
Internal sensors monitor material density during penetration, allowing the bomb to explode at optimal depth to maximize the destruction of hardened underground targets.
The weapon was originally tested using B-52 bombers but was intended primarily for B-2 deployment because stealth capability is required to reach heavily defended targets.
The bomb achieved operational capability in 2011, followed by multiple upgrades and validation tests between 2014 and 2024, including improvements to smart fuse systems for tunnel targets.
Final Production Phase Before Next Weapon System
The new procurement is expected to be the final production batch before the Air Force shifts focus to its successor weapon, known as the Next-Generation Penetrator, or NGP.
The NGP program seeks a lighter weapon, reportedly not exceeding 22,000 pounds, capable of defeating hardened and deeply buried targets using newer technologies. The Pentagon also intends to open competition to multiple suppliers rather than relying on a single manufacturer.
New contracts are structured to enable independent modification and improvement of weapon systems, encouraging innovation and reducing long-term dependence on proprietary systems.
Compatibility With Future Bombers
The shift toward a lighter penetrator also aligns with the introduction of the B-21 Raider stealth bomber, which is smaller than the B-2 and expected to carry lower payload weights.
It remains unclear whether the current MOP weapon could be integrated onto the B-21 platform, making development of a lighter successor more practical for future strategic operations.
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