Key Points and Summary – South Korea’s KF-21 Boramae is a homegrown 4.5-generation “budget stealth” fighter designed to replace aging F-4s and F-5s while offering an affordable alternative to the F-35.
-Powered by twin GE F414 engines and equipped with a Korean AESA radar, the KF-21 blends low-observable shaping with external weapons on 10 hardpoints today and planned internal bays in later blocks.
KF-21. Image Credit: Creative Commons.
-With fly-away costs around $80–100 million, it targets countries that want modern multi-role capability without full fifth-generation price tags or political strings.
-Block 2/3 upgrades could push it closer to true stealth, giving Seoul real export potential in a crowded fighter market.
South Korea’s KF-21 ‘Budget Stealth’ Fighter Aims to Beat the F-35 on Price
The KF-21 Boramae is an indigenous, 4.5-generation, “budget stealth” fighter, manufactured by KAI (Korea Aerospace Industries) to replace older fleets like the F-4 and F-5, offering a cost-effective, stealth-capable platform that blends 4th-gen features with future 5th-gen upgrades like internal weapons bays, aiming for technological independence and strong export potential against rivals like the F-35.
The KF-21 offers strong multi-role performance, high speed (Mach 1.8+), twin engines, a modern AESA radar, and significant growth potential for future stealth upgrades (Blocks 2/3) with internal weapons bays, making it a cost-effective, versatile workhorse for South Korea and potential export customers.
The South Koreans have built a 4.5-generation “budget stealth” fighter aimed squarely at countries that want advanced jets but can’t afford large F-35 fleets—or don’t want the political considerations that come with the F-35.
The Boramae is powered by twin General Electric F414 engines, equipped with an AESA radar and modern avionics. The KF-21 trades full stealth and internal bays for lower cost and easier export, bridging the gap between older 4th-generation aircraft like the F-16 and actual 5th-generation stealth fighters like the F-35.
Meet The South Korean KF-21 Boramae Fighter
The KF-21 bears more than a passing resemblance to the American-built fifth-generation stealth fighter, the F-22 Raptor, although many aviation enthusiasts liken it to the F-35.
And the resemblance to the Raptor may not be a coincidence; Lockheed Martin partnered with KAI to provide technical support with the development of the KF-21.
Regardless, both feature blended wings, twin engines, and distinctive tail configurations, optimized for aerodynamics and reducing radar cross-section (RCS). The KF-21 draws on advanced fighter design principles, incorporating elements seen in 5th-gen aircraft.
KF-21 Boramae Fighter KAI Image
KF-21 Fighter from South Korea. Image Credit: Creative Commons.
The GE F414 engines push it to Mach 1.8, but it doesn’t possess supercruise capability.
Alex Hollings wrote that the Boramae is a unique aircraft that incorporates a variety of 5th-generation (or stealth) design elements while still carrying munitions externally, as older 4th-generation platforms do.
It has 10 hard points for external munitions, including six traditional underwing hard points and four semi-recessed hard points on the underside of the fuselage to provide a slightly stealthier profile. Fully-shrouded internal weapons bays will eventually replace those recessed hard points.
The KF-21 Is Not A Stealth Fighter, Despite Its Appearance
The radar cross section of the KF-21 is approximately 1 meter; it was designed to be more stealthy than the Eurofighter Typhoon or the Rafale, but it is not a stealth fighter, where the RCS of the F-35 is superior (around 0.005 sq. meters).
The KF-21 uses an AESA radar developed by Hanwha Systems and includes infrared search-and-track capabilities and EW systems. But it isn’t the equivalent of the F-35’s AN/APG-81 AESA radar, Distributed Aperture System, Electro-Optical Targeting System, and advanced sensor fusion, which provide unmatched situational awareness.
The fly-away costs are estimated to be approximately $80-100 million per aircraft, which is why it has been dubbed South Korea’s “cheap F-35.” However, the Block 1 version has only limited internal weapons bay storage, instead relying on external hardpoints.
KF-21. Image Credit: Creative Commons.
Future versions will offer complete internal weapons bay storage. Although the design was first unveiled in early 2021 and flew for the first time in July 2022, the KF-21 is expected to enter service with the Republic of Korea Air Force (ROFAK) by the middle of 2026. The ROFAK is expected to initially have 40 KF-21s.
The KF-21 Could Find Its Own Niche
The design of the KF-21 appeals most to those countries that need …and want their air forces to have advanced capabilities, but don’t have the budgets to purchase fighters like the F-35.
The South Korean government is in talks with the United Arab Emirates (UAE) on a proposed 15 billion-dollar defense package centered on the KF-21 Boramae fighter jet, tied to joint production and co-export plans.
If this proposal can be worked out, the deal could give Abu Dhabi a next-generation multirole aircraft while expanding Seoul’s global defense share of the market.
South Korea is already ranked at 10th worldwide in arms exports, and the government has publicly set a goal of becoming the world’s fourth-largest defense supplier by 2030, exporting platforms like K2 tanks, K9 howitzers, Chunmoo rocket launchers, and FA-50 light fighters.
This will be helped by the fact that the Boramae will be capable of becoming an actual fifth-generation aircraft, with internal weapons storage, stealth coatings, and more.
But for now, it can carve out its own niche in the market. The aircraft is cheaper to buy and maintain than a fifth-generation aircraft. And of course, there would be virtually no restrictions on purchasing the fighter as compared to the F-35.
The KF-21 is a wise, pragmatic choice for countries seeking a modern, affordable, and capable fighter, especially to complement more expensive stealth aircraft like the F-35, thereby filling crucial roles in a layered defense strategy.
It’s a powerful “jack of all trades” with a clear path to becoming a more potent stealth fighter in its later blocks.
The KF-21 Boramae is a very promising design. Does it compare to the F-35? No, but for now it doesn’t have to.
About the Author: Steve Balestrieri
Steve Balestrieri is a National Security Columnist. He served as a US Army Special Forces NCO and Warrant Officer. In addition to writing on defense, he covers the NFL for PatsFans.com and is a member of the Pro Football Writers of America (PFWA). His work was regularly featured in many military publications.
