Could a country which less than ten years ago possessed no homegrown stealth fighter possibly deploy one of the world’s most tradeable fifth-generation fighters? South Korea’s KF-21 Boramae, already an impressive 4.5-generation aircraft, is on a course plan to become the KF-21EX a fully stealthy aircraft intended to compete with the F-35, Su-57, and J-35A by the early 2030s.
1. From 4.5 to 5th Generation
The KF-21 project started in 2015 as a joint venture between Korea Aerospace Industries (KAI) and Indonesia as a low-cost bridge between fourth- and fifth-generation fighters. Although Block I aircraft, which feature twin GE F414-GE-400K engines, feature semi-stealth shaping, AESA radar, and high-technology avionics, the Block III KF-21EX will have the complete set of low-observable capabilities. KAI CEO Kang Goo-Young has stated, “They say the KF-21 is a 4.5-generation fighter, but I believe that’s an underestimate. I refer to it as a 4.9-generation fighter.”
2. Internal Weapons Bays and Low-Observable Shaping
At the heart of the KF-21EX upgrade is the inclusion of twin internal weapons bays, pre-designed in the original airframe to reduce structural rework. Concept art depicts carriage of 2,000-pound-class guided bombs like GBU-31 JDAMs with BLU-109 penetrators. This transition from pylons outside the aircraft to internal carriage will significantly minimize radar cross-section, a key determinant in penetrating modern air defense systems. The KF-21EX will also have a reprofiled canopy, radome with minimized radar signature, and conformal antennas to further eliminate detection.
3. Indigenous Stealth Engine Development
South Korea is spending 86 billion won on a locally developed next-generation turbofan to power its aircraft in place of existing U.S.-made engines. Its new powerplant should include low-observable nozzles to reduce infrared emissions, enable supercruise, and increase operational range. The move is as much about performance as sovereignty less dependence on foreign suppliers for key propulsion technology.
4. Advanced Electronic Warfare and Survivability Systems
The KF-21EX will integrate its electronic warfare sensors internally in order to minimize radar wave-reflecting protrusions externally. KAI offers “survivability technologies” and next-generation situational awareness systems, possibly including AI-capable mission computers and DRFM decoys. These technologies are designed to counter more advanced threats, including Russian-provided surface-to-air missile systems recently deployed by North Korea.
5. AESA Radar: The Jet’s Eyes
Hanwha Systems has initiated mass production of its domestic AESA radar for the KF-21, producing 40 units to be delivered by 2028. Each array has approximately 1,000 transmit/receive modules, facilitating simultaneous air, ground, and sea tracking with strong jamming resistance. The electronic beam steering of the AESA enables quick multi-target engagement without mechanical action, a step ahead in capability and dependability compared to vintage radars.
6. Manned-Unmanned Teaming with Loyal Wingman Drones
The KF-21EX will be configured for manned-unmanned teaming (MUM-T), coordinated with stealthy “loyal wingman” drones like the Low Observable Unmanned Wingman System (LOWUS). On suppression of enemy air defenses (SEAD) missions, the manned fighter might serve as an escort jammer while unmanned aircraft work as stand-in jammers, with coordinated real-time sensor data for distributed targeting. A two-seat version of the KF-21EX would enable the second crew member to oversee drone command and coordination exclusively.
7. Integration of Weapons for Stealth and Versatility
In addition to heavy bunker-busters, the internal bays will be used to carry MBDA Meteor beyond-visual-range missiles, LIG Nex1’s Long-Range Air-to-Air Missile, and GBU-39 Small Diameter Bombs. Air-Launched Effects (ALE) systems are also scheduled, adding electronic attack and reconnaissance to the aircraft’s mission set. This variety of ordnance provides the KF-21EX with the ability to engage both hardened ground targets and high-value airborne targets without being detected.
8. Strategic Positioning in the International Fighter Market
With a projected price significantly lower than that of the F-35 and fewer export limitations, the KF-21EX is well-positioned to entice countries desiring fifth-generation capability without the political or financial impediments of American systems. South Korea’s established export track record with the FA-50 strengthens its ambitions. By 2032, the Republic of Korea Air Force intends to operationalize up to 120 KF-21s, with the EX variant potentially comprising a sizeable portion of that fleet.
KF-21EX’s development represents a conscious philosophy of engineering design for expansion, develop stealth incrementally, and couple manned platforms with unmanned ones for optimal operational adaptability. If realized on schedule, South Korea will become part of the exclusive group of countries operating fifth-generation indigenous fighters reshaping regional air power dynamics as well as the global defense industry.
