It’s not stealth or speed that is the largest technological hurdle to the first sixth-generation fighters yet entering service, but rather thermodynamics. The incredibly high electrical power needs of the powerplants and electronic systems on board next-gen fighter jets will require an enormous amount of electricity generation, which comes with a lot of heat. These aircraft are expected to feature stunning leaps in technology, drone interoperability, and even directed energy weapons, better known as lasers.

The Chinese defense industry was the first to fly working prototypes, but since then, the apparent progress has been slow-going, with the primary hurdle expected to be the powerplants. Meanwhile, the US is finally taking steps towards an airworthy example, but the first airframe is not expected to take off until 2028. The Future Combat Air System program has all but dissolved, but Europe’s Global Combat Air Program is on track to succeed where FCAS failed. Yet all of these initiatives face the same thermal management challenges.

The Common Ground: Defining Sixth-Generation Capabilities

Credit: BAE Systems

Sixth-generation doctrine dictates that an aircraft must not just be a shooter, but a node-based theater commander, a ghost, and an air superiority fighter all at once. Running these capabilities simultaneously demands an exponential leap in electrical generation that legacy fighter engines simply cannot physically produce.

Barring the differences in technical means to achieve greater combat capability in weapon systems, each and every next-gen fighter in development will require a massive amount of computing power on board. That alone demands exponentially more electricity than existing fighter jet engines are capable of producing.

Now consider that all of these planes need to not only power an extensive list of systems, sensors, weapons, and other equipment, but they must do so while concealing their thermal signature from enemy detection. Simultaneously, every one of these sixth-generation fighter jets is aiming to achieve a dramatically superior range than their predecessors in order to improve airspace penetration and independence from air-to-air refueling assets.

So, while doing all of that, these jets also need to be modular and have excess capacity to accommodate future systems as emerging threats dictate upgrades. That is a very tall order for any aerospace program, even the best-funded and most advanced military initiative. While the US, Europe, and China share the same thermodynamic dilemma, their industrial base, strategic priorities, and technical philosophies are leading them to fundamentally different solutions. Achieving a quantum leap in power, cooling, and range will demand ingenuity at every level.

NGAD: Uncle Sam’s Most Exquisite Warbird

Credit: US Air Force

America’s Next Generation Air Dominance program aims to construct the first sixth-generation fighter jet on US soil. Boeing was awarded the contract in early 2025 and dubbed its aircraft the F-47. While the program is accelerating rapidly after getting a late start following China’s high-visibility test flights in late 2024, the Next Generation Adaptive Propulsion program is a step behind. While the first F-47 is hoped to take flight in 2028, the variable-cycle engines that will power it may already be behind schedule.

The Department of Defense wants to run an aggressive schedule to deploy its most ‘exquisite’ fighter jet to date, as the USAF calls it. However, the NGAP program, which is currently a dual track managed by General Electric and Pratt & Whitney in parallel, is allegedly already hitting setbacks. The Air Force has cited persistent supply chain disruption to the physical testing and evaluation required to progress the GE XA102 and PW XA103 to the same level of maturity as the NGAD airframe.

The F-47 program itself has moved at an unusually rapid pace compared to traditional Pentagon acquisition cycles. The first X-Planes supporting the development of the NGAD took flight in 2019, according to the War Zone. What appeared to be a McDonnell Douglas X-36 was also just recently photographed in the sky over Area 51 performing tests.

The powerplant program is forecast to be as much as three years behind the airframe development. If the Air Force pushes ahead to get the F-47 off the ground in 2028, that means that they will have to use a conventional legacy engine or wait until 2031 to put the revolutionary third-stream engines in the first airworthy NGAD.

Beijing’s Achilles’ Heel: The Jet Engine Tech Curve

Credit: PLA MOD

The People’s Liberation Army Air Force has made significant strides with the production of the Chengdu J-20 Mighty Dragon stealth fighter jet. Production of the aircraft is ramping up to triple digits per year, with a total fleet expected to exceed 1,000 planes in the next decade. At the same time, the sixth-generation Chengdu J-36 and the Shenyang J-50 have both made their world debut in 2024. However, this also cast a spotlight on one of the greatest weaknesses of the Chinese defense industrial aerospace sector: modern jet engine production.

The Chengdu jets are particularly good examples of the technological disparity between Western bloc aerospace manufacturers and those in the People’s Republic of China. The J-20 only recently received the WS-15 jet engine upgrade, which is still not on par with that installed in the decades-old Lockheed Martin F-22 Raptor. Its inefficiency, lower performance, and lack of stealthiness make it an overall weaker platform by comparison to the Skunk Works super fighter. The J-36 notably has a third engine, which is exceptionally unusual for an aircraft classified as a fighter.

The Shenyang J-50, on the other hand, is a twin-engine tailless fighter jet. However, it is speculated that it will be a carrier-capable platform, which is why it is a smaller airframe. There’s no reflection on superior engine technology, and it likely suffers from the same limitations as its other next-gen counterparts produced in the PRC. So, while these stunning X-planes were able to get into the air before their Western counterparts, the lack of apparent progress since then is indicative of major roadblocks to their progression to an operational status.

European Remobilization: The Road Ahead For GCAP

Credit: BAE Systems

The Global Combat Air Program, initiated under the umbrella of the BAE Tempest next-gen fighter jet program, is very ambitious but shows strong promise based on the latest events. The program received billions of dollars in funding under the Edgewing multinational program management office just recently, and with FCAS relegated to a smaller scope, Germany is now considering joining, and other nations like Canada and India are also showing strong interest. Arguably, the greatest hurdle to the success of GCAP is that no European manufacturer has produced a fifth-generation fighter jet.

The GCAP program began as a trilateral production consortium between the United Kingdom, Italy, and Japan. All of these countries fly the American-made Lockheed Martin F-35 Lightning II, but none of them have domestically developed an airplane of that technological level. Still, Italy and Japan are home to the only final assembly lines for the F-35 Joint Strike Fighter outside the USA. That gives the industrial alliance some momentum, but the GCAP is a far more ambitious aircraft that parallels the capabilities of the F-47 in terms of bleeding-edge technology.

As the GCAP partners chose to buy the American F-35 rather than build an indigenous fifth-generation stealth fighter, these aerospace giants are attempting a massive two-generation technology leap. When the Skunk Works division at LM designed the F-22 and F-35, it spent 30 years discovering how punishing it is to manage heat inside a completely sealed, radar-absorbing airframe. Companies like BAE Systems, Leonardo, and Rolls-Royce have never designed a low-observable aircraft from scratch.

The F-35, in particular, famously ran into severe thermal issues with its PW F135 engine. That engine is now the cause of delay behind the Technology Refresh Three Block Four program, which has greatly reduced JSF fleet readiness around the globe. Rolls-Royce launched the Advanced Power and Propulsion System program to fundamentally redesign how an engine handles heat. Mitsubishi Heavy Industries X-2 Shinshin demonstrator and the IHI XF9 engine program can help push the consortium to the finish line, but the challenge remains daunting.

Making The Next Era In Air Power A Reality

Credit: US Air Force

In classic American fashion, the Boeing program aims to overcome the incredible demands of the sixth-generation fighter jet systems through sheer power. Once the NGAP engines are operational, they will represent a breakthrough in aerospace technology and deliver unprecedented capability to the US Air Force. The innovative new engines will also be 25% to 30% longer range, thanks to exceptional fuel efficiency and be capable of full thermal masking for true multispectral stealth.

GCAP is more likely to rely on energy management and efficient design to reduce the load on the powerplants and adaptively cut heat emissions when stealth is paramount. It is projected that through a highly efficient engine design and the integration of artificial intelligence, the GCAP will achieve multispectral stealth as required and maximum power output on demand through an active architecture. This differs from the American solution, which aims to maximize every design feature simultaneously without compromise at any point on a mission profile.

The PRC’s path forward to creating a next-gen fighter jet is less clear, with sources like The Clash report stating that variable-cycle engines are making progress while others speculate that ‘heat sink’ fuels could be the PLAAF’s strategy. The concept of using jet fuel that absorbs heat produced by the systems and then burns it as a part of the natural engine cycle harkens back to the Lockheed SR-71 Blackbird, in fact, with its famously low flashpoint fuel, which lends credence to the possibility of a workaround for the PRC’s engine tech bottleneck.