Summary and Key Points: Chinese researchers say they have found aerodynamic and stability weaknesses in the US Air Force’s B-21 Raider, and they did it without seeing a single classified document. Scientists at the China Aerodynamics Research and Development Centre fed publicly available imagery of the bomber into simulation software called PADJ-X and modeled how the aircraft would behave in flight. Their conclusion was that small changes to its configuration could theoretically improve its performance. There is a strong reason to doubt the finding and a stronger reason to pay attention to the method — because a flying wing like the B-21 is deliberately built to be aerodynamically unstable, held in controlled flight by its flight-control computers, and instability that looks like a defect in a model is the design working as intended.
The B-21 Raider Has a Flaw, Says China?
Months ago, Chinese aerospace researchers said they have identified potential aerodynamic and stability weaknesses in the US Air Force’s next-generation stealth bomber, the B-21 Raider.
The claim comes from a study conducted at the China Aerodynamics Research and Development Centre, one of China’s major military aviation research institutions.
Using a newly developed simulation software, PADJ-X, Chinese researchers modeled the bomber’s likely flight characteristics based on publicly available design information.
The study reportedly identified possible improvements to the B-21’s aerodynamic configuration—suggesting that the PADJ-X software can analyze complex military aircraft designs.
The findings, of course, are still theoretical, but the research highlights the growing role of advanced computational modeling in modern military competition.
What the B-21 Raider Is
B-21 Raider. Image Credit: USAF.
B-21 Raider Taking on Fuel. Image Credit: U.S. Air Force.
The B-21 Raider is the US’s next-generation strategic stealth bomber. Currently under development by Northrop Grumman, the B-21 can be considered a replacement for the company’s most recent stealth bomber, the B-2 Spirit.
Appropriately, once the B-21 is available, it will replace both the B-2 and the B-1B Lancer, marking the most dramatic change to the Air Force’s bomber corps in a generation.
A U.S. Air Force B-1B Lancer prepares to refuel behind a KC-135 Stratotanker during a bomber air demonstration over the U.S. Southern Command area of responsibility Oct. 23, 2025.
The demonstration showcased Southern Command’s ability to quickly mobilize and enable the rapid establishment of credible, combat-ready forces with effective and overwhelming force.(U.S. Air Force photo by Airman 1st Class Daniel Harrell)
B-21’s Key Characteristics
The B-21’s (publicly known) key characteristics include a stealth-focused flying wing design that is outwardly very similar to the B-2’s.
The B-21 is being designed for long-range penetrating strike capability, which the flying wing design facilitates through improved fuel economy (thanks to low drag) and reduced radar cross-section/improved stealth performance (thanks to limited control surfaces). The B-21 will carry both conventional and nuclear weapons, as well as advanced sensors and network connectivity.
The aircraft is intended to operate in heavily defended airspace, penetrating advanced air defense networks in potential conflicts with near-peer powers such as China or Russia.
And although many of the B-21’s technical details remain classified, the B-21 is expected to represent a major leap forward in stealth, survivability, and digital integration compared to the B-2.
B-2 Spirit Stealth Bomber. 19FortyFive.com Photo from National Museum of the U.S. Air Force Visit in 2025.
The Chinese Study
According to the research summary, Chinese scientists used a simulation platform called PADJ-X to model the B-21’s aerodynamic behavior.
The software reportedly enables engineers to analyze aircraft performance through high-fidelity digital simulations rather than expensive wind-tunnel tests.
Using theoretical modeling based on open-source imagery and assumptions about the bomber’s design, researchers evaluated potential stability and aerodynamic characteristics of the B-21.
Aspects the Chinese examined include: airflow around the bomber’s flying-wing configuration; stability across different flight regimes; aerodynamic efficiency; and potential structural or performance trade-offs.
The research suggested that small changes in the aircraft’s configuration could theoretically improve performance.
Limits of the Analysis
However, the study should be taken with a grain of salt, as the analysis is based entirely on external modeling rather than classified design data. The B-21’s exact aerodynamic configuration, materials, and flight control systems remain highly classified.
This means that Chinese researchers are working from public imagery and educated assumptions—not from detailed engineering data from the actual aircraft.
Also worth noting: modern stealth aircraft are often inherently unstable and rely on advanced flight-control computers that can compensate for aerodynamic instabilities that might appear problematic in purely theoretical models, thereby allowing the aircraft to maintain controlled flight.
The B-21 Raider was unveiled to the public at a ceremony December 2, 2022 in
Palmdale, Calif. Designed to operate in tomorrow’s high-end threat environment, the B-21 will play a critical role in ensuring America’s enduring airpower capability. (U.S. Air Force photo)
Which is to say that any Chinese claims about “flaws” in a forthcoming US aircraft, the development of which has been a closely guarded secret, should be treated with skepticism.
Common Practice
Despite the limitations of the Chinese study, the research highlights a common practice in military aerospace competition: countries routinely analyze the visible design characteristics of rival aircraft to estimate performance and identify potential weaknesses.
Failing to engage in such behavior and critique would be negligent from a security perspective.
And the use of tools like PADJ-X reflects a broader shift toward digital engineering and advanced simulation in aerospace design. High-performance computing enables engineers to test aircraft designs virtually before building physical prototypes, accelerating design cycles, reducing development costs, and enabling the safe testing of extreme flight scenarios.
Artist rendering of a B-21 Raider concept in a hangar at Dyess, Air Force Base, Texas, one of the future bases to host the new airframe. (Courtesy photo by Northrop Grumman)
China’s interest in the Raider is no surprise, either; it reflects the broader strategic competition between the US and China.
Long-range stealth bombers remain one of the most important tools for projecting military power.
China, too, is currently believed to be developing its own next-generation stealth bomber, the Xi’an H-20, any development of which the Americans will watch closely, waiting to feed data into their own performance modeling software.
About the Author: Harrison Kass
Harrison Kass is an attorney and journalist covering national security, technology, and politics. Previously, he was a political staffer and candidate, and a US Air Force pilot selectee. He holds a JD from the University of Oregon and a master’s in global journalism and international relations from NYU.
