CaliToday (13/9/2025): South Korea is pushing forward with comprehensive upgrades for its KF-21 Boramae fighter program, aiming to transform the domestically-produced aircraft into a complete fifth-generation stealth platform.
The ambitious plan includes the development of internal weapons bays, advanced stealth materials, and a next-generation engine developed entirely in-country.
According to South Korea's proposed 2026 defense budget, the government is allocating expanded funding to support the long-term development of stealth capabilities for the KF-21 and other advanced aviation systems. Korea Aerospace Industries (KAI), the manufacturer of the KF-21, is currently finalizing the Block I development phase while concurrently working to implement conceptual Block II and Block III upgrades.
The Block III version, as envisioned by KAI, will take the KF-21 beyond its current limited-stealth configuration by integrating missiles and sensors internally within the fuselage—similar to the American F-35 Lightning II. This design change will minimize the jet's radar cross-section and enhance its survivability in contested environments.
The government's proposal includes 86 billion won ($62 million) to initiate the development of an advanced domestic jet engine, and an additional 630 billion won ($453 million) for stealth-related sensor and material technologies. If successful, this new engine could eventually replace the current US-supplied GE F414-GE-400K turbofans.
KAI has stated it aims to complete Block I development by the end of 2026, followed by expanded air-to-ground capability testing leading to Block II. For Block III, the company plans to introduce the full stealth configuration with internal bays capable of carrying four Meteor-class air-to-air missiles or precision-guided bombs. The aircraft will also feature an integrated electronic warfare system and a redesigned internal optical targeting pod, replacing the current external pods.
The push for stealth is not limited to the airframe design. South Korea's Ministry of National Defense is also pursuing the development of a long-range air-to-air missile analogous to Europe's Meteor missile, which is already being integrated with the KF-21. This indigenous missile is expected to feature a ramjet propulsion system, enabling extended range and sustained high speed in its terminal phase.
The upgraded KF-21 will eventually be integrated with unmanned "loyal wingman" aircraft, with plans to build a high-speed, high-capacity data link that allows the lead aircraft to coordinate teams of autonomous drones. In contested airspace, the drones could be used to spoof enemy air defenses or conduct strikes, allowing the manned fighter to maintain a safe distance.
South Korea's development strategy reflects a growing emphasis on defense self-sufficiency. The Defense Acquisition Program Administration (DAPA) and KAI are also prioritizing engine domesticity to avoid future supply chain constraints. Hanwha Aerospace and Doosan Enerbility are leading the development of a new 16,000-pound-thrust turbofan engine, with a smaller, 5,500-pound demonstrator version expected to begin testing later this year.
Beyond the aircraft and its engine, the Ministry of National Defense has earmarked 7.5 trillion won (approx. $5.4 billion) through 2033 to fund the development of the new air-to-air missile. The ministry stated that this system is expected to outperform the US-made AIM-120 AMRAAM, particularly during the final engagement phase.
However, the effort is not without its challenges. Developing a ramjet-powered missile or a modern stealth jet engine carries a high degree of technological risk and could take decades to perfect. The Meteor missile program, for instance, took over 25 years to become operational, despite being a multi-national effort by experienced European defense firms.
South Korea's experience in drone and turbofan development, combined with potential support from international partners, could help mitigate some risks. However, observers warn that delays and cost overruns are still possible.
By transforming the KF-21 into a fully stealth-capable platform, Seoul aims not only to bolster its air power but also to build a competitive aerospace industry capable of exporting a next-generation fighter jet—similar to Turkey's approach with its Kaan stealth jet.
If the program proceeds as planned, the KF-21 Block III could represent a major milestone: South Korea's first indigenous stealth fighter, bridging current tactical needs with the future of unmanned teaming and long-range precision warfare.
