U.S. Next-Gen Fighter Jet Engine Program Enters Prototype Stage

America’s race for air superiority is entering a new phase, with next-generation fighter jet engines reaching the prototype stage. The U.S. Air Force has been pouring resources into the Next Generation Adaptive Propulsion (NGAP) program, where aerospace giants General Electric and Pratt & Whitney are competing to develop revolutionary powerplants—the XA102 and XA103 engines—for the sixth-generation Next Generation Air Dominance (NGAD) fighter.

However, as excitement grows around these cutting-edge technologies, a critical question surfaces: Could these next-gen fighter jet engines also serve as replacements for the aging and problematic F-35’s Pratt & Whitney F135 engine?

If so, it could dramatically enhance the F-35’s combat effectiveness, but the feasibility, cost-effectiveness, and long-term value of such an upgrade remain points of intense debate among defense analysts and military planners.

Current Developments

In January 2025, the U.S. Air Force substantially increased funding for the NGAP program, elevating contract ceilings for both General Electric and Pratt & Whitney from $975 million to $3.5 billion each. This financial boost aims to support the design, testing, and prototype fabrication of next-generation fighter engines, with completion anticipated by July 2032.

Both General Electric’s XA100 and Pratt & Whitney’s XA101 engines have successfully passed their Detailed Design Reviews (DDR)—a critical step before full-scale prototype testing. While lab tests have validated their efficiency, flight testing remains uncertain, leaving questions about how soon these engines will move from concept to combat.

The NGAP program is centered on developing adaptive cycle engines, which can adjust operational modes in flight to optimize performance based on mission requirements. General Electric’s XA100 engine, for example, boasts approximately 25% greater fuel efficiency and 10-20% more thrust compared to the existing F135.

These advancements are designed to enhance range, speed, and combat endurance for future air dominance platforms like the NGAD fighter. However, with these capabilities, speculation has grown: could these engines also be integrated into the F-35 fighter jet?

These questions are becoming more pressing as the F-35 faces persistent engine issues. Once hailed as the backbone of U.S. and allied air forces, the F-35’s Pratt & Whitney F135 engine is showing its limitations. Overheating, power deficiencies, and durability concerns are increasingly problematic—especially as future upgrades, such as Directed Energy Weapons, demand more energy.

Maintenance is another major concern. The F135 engine’s frequent repairs due to thermal stress are driving up sustainment costs and reducing operational availability. This has sparked debates over whether to upgrade the F135 engine with an Engine Core Upgrade (ECU) or pursue an entirely new propulsion system. While upgrading the existing engine is more cost-effective in the short term, it may not fully resolve long-term performance limitations.

With NGAP prototypes now advancing, the XA100 and XA101 engines offer a potential solution. These engines promise better fuel efficiency, extended range, and increased thrust—capabilities that could breathe new life into the F-35  and potentially transform it into a more lethal and capable fighter for decades to come.

Read more about the XA100 engine here!

Could Sixth-Gen Engines Power the F-35?

The idea of equipping the F-35 with a sixth-generation adaptive engine is gaining traction, but is it practical? There are compelling arguments on both sides.

The Case for Upgrading

A more advanced engine like the XA100 or XA101 could significantly enhance the F-35’s range and fuel efficiency, allowing pilots to stay in combat zones longer without refueling. This is crucial for long-range operations in the Pacific, where extended flight endurance is a strategic necessity. Additionally, greater thrust would improve the jet’s maneuverability, making it more effective in dogfights and high-threat environments.

Perhaps most importantly, a next-generation engine could future-proof the F-35, providing the additional electrical power needed for upcoming Directed Energy Weapons (DEWs), electronic warfare systems, and enhanced radar capabilities. Without this, the jet risks becoming outdated just as peer adversaries like China and Russia field their own advanced fighters.

Want to know more about the F-35? Watch this video Many Things You Probably Didn’t Know About F-35 Fighter Jet

The Case Against It

Despite these advantages, integrating a sixth-generation engine into an older airframe like the F-35 presents serious logistical and financial challenges. The airframe wasn’t designed for an adaptive-cycle powerplant, meaning major modifications could be required—driving up costs and delaying fleet readiness.

Read: USAF Rethinks Next-Gen Fighter: Considers Cheaper Alternatives

There’s also the issue of development priorities. The Pentagon’s main focus is on the Next Generation Air Dominance (NGAD) program, which is set to define the future of U.S. air superiority. Slowing down NGAD to retrofit the F-35 could be seen as a step backward.

Moreover, the U.S. Air Force has opted for an Engine Core Upgrade (ECU) for the existing F135 engine rather than a complete replacement. This approach aims to enhance the engine’s performance to meet the F-35’s evolving requirements without the complexities associated with integrating an entirely new engine.

This decision reflects a pragmatic approach to balancing performance improvements with cost and logistical considerations, ensuring the F-35 remains operationally viable without disrupting ongoing development efforts.

Finally, even if the technology proves viable, would Congress be willing to fund it? The F-35 program has already faced intense budget scrutiny, and lawmakers might be hesitant to approve billions of additional dollars for an engine overhaul when a cheaper F135 upgrade is on the table.