The U.S. Air Force Wants New ‘Bunker Busters’ to Destroy Deep Targets

If a target is buried under rock, wrapped in reinforced concrete, protected by air defenses, and designed by engineers who assume America owns a lot of bombs, the answer cannot simply be, “Well, drop a regular one harder.” Deep targets are built to survive exactly that kind of thinking. They are the military equivalent of a bank vault hidden under a mountain and covered by a second, angrier bank vault.

That is why the U.S. Air Force’s interest in new bunker busters matters. This is not just a story about building a bigger bomb because the old one no longer looks dramatic enough in Pentagon briefings. It is a story about how underground warfare is changing, how adversaries are burying command nodes, missile infrastructure, weapons programs, and storage sites deeper than before, and how the Air Force is trying to create a more flexible family of weapons to deal with them.

The conversation starts with the famous GBU-57 Massive Ordnance Penetrator, or MOP, the 30,000-pound heavyweight that has become America’s best-known bunker-busting weapon. But the real story no longer ends there. The Air Force is also working with the 5,000-pound GBU-72, continuing upgrades to MOP itself, and pushing ahead with a successor called the Next Generation Penetrator. In plain English: the service wants more options, more flexibility, and more ways to ruin the day of anything hiding deep underground.

Why the Air Force Still Cares So Much About Deep Targets

Hard and deeply buried targets have long been one of the military’s most stubborn headaches. They are not just underground rooms. They are purpose-built facilities designed to absorb punishment, confuse targeting, and protect the people or equipment inside long enough to keep operating. Think mountain bunkers, tunnel complexes, buried command centers, and sensitive weapons sites that were never intended to be vulnerable to ordinary airpower.

That challenge is not going away. If anything, it is becoming more central to modern warfare. Rivals have studied American precision strike for decades. They know how well the United States can destroy exposed aircraft shelters, fuel farms, radar sites, and surface facilities. So they bury the most valuable stuff deeper. The lesson is painfully simple: when America gets better at hitting targets, adversaries get better at hiding them.

For the Air Force, that creates a planning problem. It is not enough to have one spectacular penetrator for the absolute toughest target. The service also needs scalable options for different kinds of hardened facilities, different aircraft, different ranges, and different campaign tempos. A 30,000-pound bomb is terrifying, but it is not a Swiss Army knife. It is more like a sledgehammer with a doctorate.

The Current King of the Category: MOP

The GBU-57 MOP exists because the Air Force has had a long-standing requirement to attack deeply buried facilities. It traces back to development work by the Defense Threat Reduction Agency and the Air Force Research Laboratory, and it was built specifically to go after targets that smaller weapons might damage but not decisively defeat. It is a precision-guided penetrator, not just a massive explosive lump. Its whole purpose is to survive impact, burrow into the target area, and then detonate where the damage actually counts.

That last part is important. Bunker-busting is not merely about blast. It is about sequencing. The weapon has to strike at the right angle, at the right speed, with the right structural integrity, and explode at the right point after penetration. Otherwise, you get a very expensive crater and a still-angry target buried beneath it.

MOP’s reputation grew even larger after Operation Midnight Hammer in 2025, when the weapon saw its first operational use. That moment did two things at once. First, it proved that the weapon had moved from theory to combat. Second, it reminded everyone that even America’s biggest conventional penetrator is not a magic wand. Deep targets remain incredibly hard to assess, even after a successful strike. You can bomb the mountain, but you still need to know what happened inside the mountain.

MOP’s Strengths Are Real

MOP remains the Air Force’s answer for the nastiest underground problem sets. It brings enormous mass, deep-penetration design, precision guidance, and a warhead built for hardened targets. It is the kind of weapon that exists because somebody looked at an underground facility and said, “Fine, we’re going through it.”

The Air Force has also kept improving it. Public reporting has shown continued work on smart-fuze capabilities, integration fixes, testing, sustainment, and other enhancements intended to improve how MOP performs against hard and deeply buried targets, especially where threat intelligence may be incomplete. That matters because underground warfare is full of uncertainty. The target may not be exactly where planners think it is. The void may be deeper, offset, or more heavily reinforced than expected. The weapon has to do more than arrive; it has to make sense of a very nasty arrival.

But MOP Also Has Limits

Here is the catch: MOP is not an all-purpose answer. The B-2 is the only aircraft operationally configured to carry it today, and that alone tells you a lot. If a weapon can only be delivered by a very small fleet of stealth bombers, the nation does not have an unlimited supply of shots. The weapon is powerful, but it is also specialized, logistically demanding, and tied to one elite delivery platform.

That makes MOP ideal for the hardest high-value targets, but less ideal as the only tool in the toolbox. Military planners hate one-tool solutions because real campaigns are messy. You may need repeated strikes. You may need more weapons per sortie. You may want a penetrator that can be used by other platforms. You may need something that is still serious, still ugly, still very bad news for a bunker, but not so large that it belongs in a class by itself.

The Middleweight Option: GBU-72

This is where the GBU-72 becomes interesting. It is a 5,000-pound penetrator developed to address hardened, deeply buried target challenges, and the Air Force has described it as being designed for both fighter and bomber aircraft. That alone makes it strategically attractive. It suggests a weapon that can bridge the gap between classic bunker busters and the monster-class MOP.

In theory, that gives commanders more flexibility. Not every buried target requires the biggest penetrator in the inventory. Some targets are tough but not mountain-deep. Some are numerous. Some are time-sensitive. Some are best attacked by aircraft that are more available than a B-2. A 5,000-pound penetrator with better lethality than legacy weapons can be extremely valuable in that middle ground.

And middle ground matters. Defense planning is often obsessed with the most extreme scenario, because that is where the headlines live. But war is full of second-tier, third-tier, and “we need this gone before sunrise” targets. A weapon like GBU-72 can give the Air Force a practical way to hit hardened structures without using its most exotic asset every single time. Think of it as the difference between using a wrecking ball and using a much smarter, faster demolition crew that still shows up with steel-toed boots.

The Air Force’s Real Prize: A Next Generation Penetrator

The clearest sign that the Air Force wants more than incremental improvement is the move toward the Next Generation Penetrator, or NGP. In 2025, the service awarded a prototype contract to Applied Research Associates, with Boeing involved on the team, to develop subscale and full-scale versions of the future weapon. That was not the language of a maintenance program. That was the language of replacement and redesign.

Public reporting around the effort strongly suggests the Air Force is chasing a penetrator that can succeed MOP without simply cloning it. That implies a weapon that is still built for hard and deeply buried targets, but potentially with better integration, smarter fuze behavior, more adaptable packaging, and perhaps less dependence on a single giant format. In other words, the Air Force may be asking a very modern question: can we get nearly as much underground misery with more operational flexibility?

If so, that would be a major shift. MOP was designed for a particular era of deep-target anxiety. NGP appears aimed at an era where the Air Force needs to strike more types of hardened targets across more contested theaters, while also thinking about survivability, bomber availability, inventory depth, and future aircraft like the B-21 Raider.

Operation Midnight Hammer Changed the Debate

Real-world use tends to end abstract arguments very quickly. After Operation Midnight Hammer, bunker busters were no longer just the stars of test footage and graphics packages. They were central to a high-profile strike mission against deeply buried nuclear-related sites. The operation highlighted the Air Force’s reach, the B-2’s value, and the fact that the United States remains uniquely capable of delivering the heaviest conventional penetrators against some of the world’s hardest targets.

But the operation also reinforced a less cinematic truth: damage assessment on underground facilities is maddeningly difficult. Analysts can see entry points, surface collapse, dust, heat, and disturbed terrain. They can study satellite imagery and compare before-and-after conditions. What they cannot do immediately is walk through a deeply buried facility and calmly take notes like a home inspector with a flashlight and a clipboard.

That uncertainty is precisely why the Air Force wants better effects, better fuzes, better modeling, and better penetrators. When the target is deep, the margin for error is thin. You are not trying to wreck the driveway. You are trying to break the machinery, personnel, and protected space that exist somewhere under layers of geology and engineering. That is a nasty technical problem, and it stays nasty even when the strike looks successful from orbit.

What New Bunker Busters Probably Need to Do

Based on the Air Force’s visible priorities, tomorrow’s bunker busters will not just be judged by size. They will be judged by how intelligently they behave. Fuze logic matters. Tail-kit integration matters. Software matters. Modeling and simulation matter. Test infrastructure matters. This is one of those defense stories where the glamorous part is a huge bomb, but the decisive part may be a quiet engineer tweaking timing, impact geometry, and guidance behavior.

The service also appears to care about production and sustainment more than in the past. Public documents and reporting show ongoing work on readiness, reliability, obsolescence, component support, and testing timelines. That sounds bureaucratic because it is bureaucratic. It is also how combat capability actually survives. No military wants its most important penetrator program held together by heroics, expired parts, and the national security equivalent of duct tape.

A future penetrator must also fit a larger campaign logic. Deep-target strike is not just about one bomb meeting one bunker in a dramatic moment. It requires intelligence, mission planning, stealth or stand-in access, suppression of air defenses, battle damage assessment, and often the ability to follow up. The best penetrator in the world is still part of a larger system. Without that system, it is just an expensive way to make geologists very nervous.

Strategic Risks Are Part of the Story Too

It is tempting to frame bunker busters as a pure technology success story: bigger, smarter, deeper, better. But that skips the strategic risks. Strikes against underground facilities can escalate conflicts fast, especially when those facilities are tied to nuclear programs, command authority, or strategic deterrence. They can also create false confidence. A mountain can be punched; that does not necessarily mean every critical function beneath it has been eliminated.

There is also the enduring problem of adversary adaptation. Once the United States demonstrates a deeper-penetration capability, rivals can respond by dispersing assets, improving deception, building more layers, moving material in advance, or creating multiple redundant sites. The offense-defense cycle never sleeps. It just digs.

Experience From Testing, Planning, and Real-World Use

Experience is where this story gets especially revealing. It is one thing for the Air Force to say it wants new bunker busters. It is another to see how much work sits behind that seemingly simple sentence. Deep-strike capability is not built in a weekend and it is not perfected by a single successful test. It grows out of years of design, modeling, target construction, flight testing, platform integration, and the sort of patient technical adjustment that rarely becomes a headline.

MOP itself is a case study in that long arc. Its roots go back more than two decades, and even after entering the force, the weapon continued to receive upgrades. Public reporting around smart-fuze work, integration fixes, and follow-on testing shows that bunker-busting capability is not static. The Air Force has had to keep learning from each phase: how the bomb behaves on release, how it performs against increasingly realistic targets, how the aircraft interfaces with it, and how to improve effects when target intelligence is incomplete. In this mission set, the bomb body is only part of the answer. The logic behind the detonation can be just as important.

That experience also highlights an often-overlooked issue: test realism is hard and expensive. Reprogramming documents have shown delays tied to target design and construction for smart-fuze testing. That may sound like bureaucratic wallpaper, but it is actually a big deal. If you are building a penetrator to defeat a buried target, you need representative targets to prove it works. You cannot really validate underground effects by politely dropping a bomb into an easy sandbox and declaring victory. The target itself has to be hard, buried, instrumented, and credible.

Then there is the lesson from Operation Midnight Hammer. The first operational use of MOP did not just prove the bomb could be used in combat; it showed how much choreography deep strike requires. The attack reportedly involved a large supporting force, careful route planning, stealth bombers, other precision weapons, and tailored fuzing. That should remind anyone watching that a bunker buster is not a stand-alone miracle object. It is the sharp end of a much larger spear.

Another lesson is inventory pressure. Once a unique weapon is used in real operations, restocking, sustainment, and production suddenly become urgent instead of theoretical. The Air Force’s visible interest in component support, fuze development, and future prototyping suggests the service understands that hard-target defeat cannot rely on a boutique arsenal forever. If the mission is enduring, the industrial base has to be enduring too.

Finally, experience teaches humility. Even after a powerful strike, underground targets can remain difficult to assess. Material may be relocated. Tunnel geometry may absorb or redirect effects. Critical functions may be degraded rather than destroyed. That ambiguity does not make penetrators irrelevant. It makes good penetrators, good intelligence, and good follow-on planning even more important. In a strange way, the strongest argument for better bunker busters is not confidence. It is uncertainty. The deeper the target, the less room there is for guesswork.

Conclusion

The U.S. Air Force wants new bunker busters because underground warfare is no longer a niche problem. It is a central one. America’s current penetrator arsenal still matters a great deal, especially the MOP, but the service is clearly moving toward a broader and more modern hard-target toolkit. That means improving MOP, using GBU-72 for part of the mission, and building a Next Generation Penetrator that can hit deep, hard targets with greater flexibility.

The deeper lesson is even bigger than the bomb itself. This is about how airpower adapts when the enemy buries the most important parts of the fight. The Air Force is not just chasing a heavier warhead. It is chasing a better answer to one of modern warfare’s oldest questions: how do you reach something that was built specifically so you cannot? The answer, apparently, is with smarter penetrators, smarter planning, and a refusal to let mountains feel too comfortable.