Korean next-generation fighter(KF-XX) equipped with an indigenous next-generation aircraft engine 
From KF-21 to 6th Generation: Long-Term Planning Begins
This push traces back to 2021, when the ROK military completed a research project outlining potential 5th- and even 6th-generation development paths based on the KF-21 Boramae. Although officially categorized as a 4.5-generation platform, the KF-21 incorporates a low-observable airframe design, advanced sensors, and avionics that allow future upgrades to true 5th-generation performance. During the same period, the ROK Air Force(ROKAF) commissioned a study titled “Mission Effectiveness Analysis of a ROK Manned-Unmanned Combat Aircraft Teaming System and Approaches to Building the Next-Generation Fighter.” The service emphasized that because fighter acquisition cycles exceed 15 years, it must begin planning now for a post-KF-21 system, including 5th-generation-plus systems built around manned-unmanned teaming.

Why the ROKAF Needs a New Domestic Fighter

ROKAF’s fleet of more than 160 F-16s and KF-16s will begin facing retirement decisions in the 2030s. ROKAF previously planned to operate upgraded KF-16s until around 2038. Given that fighter development and testing typically require more than a decade, officials argue that preparations for the next fighter must begin immediately. Unlike the KF-21 program—which adopted a hybrid model in which the airframe and avionics were developed domestically while the engine and weapons were sourced from abroad—the next-generation fighter will take a different approach. Unlike the KF-21 program—which adopted a hybrid model in which the airframe and avionics were developed domestically while the engine and weapons were sourced from abroad—the next-generation fighter will take a different approach.

Engine First: A New Strategy for Korea’s Next Fighter

According to aerospace industry sources, the first step of the next-generation fighter program—informally known as KF-XX—will be development of a fully indigenous engine. The KF-21 Block I/II aircraft currently entering production will use GE’s F414-GE-400K engines. In contrast, the new KF-XX engine aims to surpass the F414’s military power output by more than 3,000 lbf, targeting 16,000 lbf of thrust without afterburner. Such output would meet the requirements of a 5th- or 6th-generation fighter capable of supercruise, enhanced payload, and advanced manned-unmanned teaming operations.

A Highly Exclusive Technology Club

Only a handful of nations—the United States, United Kingdom, France, and Russia—possess complete fighter engine technology. Modern engines require materials and systems that operate above 2,000°C, including single-crystal turbine blades, advanced superalloys, ceramic-matrix composites (CMCs), high-pressure compressors, stable high-temperature combustors, variable-geometry nozzles, and thrust-vectoring technology. These technologies are tightly protected under the U.S. International Traffic in Arms Regulations (ITAR), making foreign transfer nearly impossible.

Key Domestic Technologies South Korea Must Master

South Korea’s defense industry identifies several priority technologies: Single-crystal turbine blades, Superalloys and ceramic-matrix composites (CMCs) for high-temperature turbine stages, High-pressure compressor aerodynamics Combustor technology capable of stable operation at extreme heat Variable-area nozzles and thrust-vectoring mechanisms Achieving these capabilities would allow Korea to directly shape its future fighter’s performance while dramatically reducing overseas maintenance and parts costs—boosting export competitiveness.

Industry Players Involved

Globally, GE, Pratt & Whitney, Rolls-Royce, and Safran dominate the aircraft engine market through proprietary materials and foundational technologies. In South Korea, Hanwha Aerospace, LIG Nex1, and Korea Aerospace Industries (KAI) are expected to lead development of core subsystems, components, and integration.

Toward a Fully Indigenous 5th–6th Generation Fighter

If successful, South Korea’s push for engine autonomy will enable the country to build a truly domestic next-generation fighter—potentially its first fully sovereign 5th- or 6th-generation combat aircraft. The effort marks a strategic shift from reliance on foreign propulsion to a long-term vision of aerospace self-reliance, positioning South Korea as a future contender in the global high-performance fighter market.

K-DEFENSE NEWS | Strategic Analysis Desk