The US Air Force has doubled its B-21 Raider test fleet, flying a second prototype in a milestone that signals faster progress toward its next-generation nuclear and conventional strike arm.
This month, multiple media sources reported that the US Air Force confirmed the maiden flight of its second B-21 stealth bomber, marking a significant milestone in testing the next-generation aircraft.
The bomber, built by military contractor Northrop Grumman, took off from Plant 42 in Palmdale, California, before landing at Edwards Air Force Base, where the B-21 Combined Test Force is based, the reports said.
With two prototypes now flying, the service can now shift from basic flight checks to evaluating weapons integration, mission systems and maintenance operations.
US Air Force Secretary Troy Meink said the additional aircraft “gains substantial momentum” for the test program. At the same time, Chief of Staff General David Allvin called it key to accelerating fielding timelines.
According to the US Air Force, the B-21 is a key part of modernizing the US nuclear arsenal. It’s designed to deliver both conventional and nuclear weapons in penetrating strike missions in enemy territory.
The US Air Force plans to buy at least 100 B-21s, replacing the B-1B and B-2 bombers with upgraded B-52Js. Each plane is expected to cost around US$700 million.
The B-21’s relatively rapid development reflects a belief that only new stealth bombers have the persistence, payload and flexibility to strike mobile launchers, bunkers and command centers in heavily defended areas.
In a nuclear role, the B-21 may be armed with the B61-13 gravity bomb, designed to destroy hardened or large area targets. Targets could include China’s massive “Beijing Military City,” an underground complex built to shelter its leadership in nuclear war.
In a conventional role, the B-21 may be armed with the Next Generation Penetrator (NGP) to attack deeply buried targets beyond the reach of the current GBU-57 Massive Ordnance Penetrator (MOP). Possible targets may include hidden North Korean missile bases, such as the Sinpung-dong Missile Operating Base near the Chinese border.
Still, it could take several years before the B-21 fleet is fully operational. In an August 2025 virtual talk for the Air & Space Forces Association’s Mitchell Institute for Aerospace Studies, US Air Force Lieutenant General Andrew Gebara noted that the US Air Force is taking its time with B-21 development.
“So this is an event-based process, based on the test team, the contractor and the program office. I believe it will happen by the end of the year, but we’re not going to ever give them an artificial date that they have to make if it doesn’t bring the test program along to where they need to be,” said Gebara.
“We’re going to proceed as we can, efficiently, effectively and with a sense of urgency, but we’re also going to be event-based,” Gebara added.
As development continues, China has already begun gaming out counters. In November 2023, the South China Morning Post (SCMP) reported that Chinese researchers from Northwestern Polytechnical University in Xian simulated an air battle between the B-21 and its latest fighter and drone technologies, resulting in the aircraft’s shoot-down. The simulation was published in the peer-reviewed journal Acta Aeronautica et Astronautica Sinica.
According to SCMP, a Chinese supersonic stealth fighter with a “conformal skin” capable of detecting the subsonic B-21’s heat and electrical signals, along with a loyal wingman drone, launched an air-to-air hypersonic missile at the B-21.
The report states that while the B-21 detected the missile launch and made evasive maneuvers, the attack mission was directed to another air-to-air hypersonic missile going for the B-21’s loyal wingman drone. It mentions that the B-21, not expecting the Chinese missile to be able to switch targets on the fly, failed to evade and was shot down.
The simulation raises more questions than answers, and China’s opaque modernization makes such claims difficult to verify. Furthermore, such assertions follow a familiar pattern—published in academic journals to add credibility and then picked up by international media outlets—amplifying China’s strategic messaging.
Despite that caveat, it is reasonable to assume that no stealth aircraft, such as the B-21, is 100% invisible.
It remains unclear whether the B-21 will perform better against evolving Chinese or Russian air defenses compared to how the old B-52, B-1, and B-2 bombers did during the Cold War and immediately afterward, against enemies with basic or outdated air defenses. This problem can be circumvented by nuclear ballistic missile submarines (SSBNs), which could be prepositioned right at an adversary’s doorstep.
They are also dependent on possibly vulnerable bases. Timothy Shugart III and Tim Walton mention in a January 2025 Hudson Institute report that the US Air Force’s decision to forgo hardened aircraft shelters (HASs) for the B-21 bomber fleet—opting instead for prototype sunshade-style “environmental protection shelters”—is a critical mistake that leaves these strategic assets exposed to drones, cruise missiles, and precision strikes.
They note a single hardened shelter costs just $30 million, a fraction of a B-21’s price, and argue that without such passive defenses, even small salvos could cripple the fleet on the ground, endangering US global strike capability.
Those vulnerabilities may limit the utility of strategic bombers to signaling over delivering nuclear strikes, when SSBNs and intercontinental ballistic missiles (ICBMs) arguably offer better survivability, extended deterrence and second-strike capability. Beyond basing risks, analysts warn the B-21 could also be overextended in nuclear operations.
Eli Glickman and Robert Peters point out in a Heritage Foundation article this month that the B-21 faces significant limitations in a protracted conventional war involving tactical nuclear weapons.
China’s rapid expansion of its nuclear arsenal and Russia’s nuclear posture emphasize the role of tactical nuclear weapons as a means to offset conventional battlefield inferiority, as opposed to strategic nuclear weapons, which aim to destroy an adversary’s war-making capability (i.e., political, industrial and population centers).
Glickman and Peters say that because US tactical nuclear weapons would almost certainly require delivery by stealth bombers, B-21s would have to be diverted from conventional operations, severely slowing US campaigns.
They point out that generating even a single strike would require large fleets of tankers and airborne warning and control system (AWACS) aircraft, pausing conventional air operations for days.
With few non-strategic nuclear options available, Glickman and Peters point out that the US could manage only one or two limited nuclear strikes before resorting to strategic weapons, raising escalation risks with China and Russia.
The B-21’s advance into testing marks more than progress in hardware—it sets the stage for a high-stakes contest over whether stealth bombers can still justify their role against evolving Chinese and Russian defenses, or whether SSBNs and ICBMs will prove the surer bet.