PUBLISHED on August 12, 2025, 08:52 AM EDT – Key Points and Summary South Korea is advancing its aerospace independence with the KAI KF-21 Boromae (“Fighting Hawk”), its first homegrown advanced fighter jet.
-Developed to replace aging U.S.-made aircraft, the KF-21 is a 4.5-generation fighter that incorporates “semi-stealth” features and bears a resemblance to the F-35.
-While not yet operational, the program is on track for full-scale production, with 40 jets scheduled for delivery by 2028.
-An even more advanced KF-21EX variant with internal weapons bays is planned, which will push the platform into a true fifth-generation stealth classification.
The KF-21 Has Arrived
For most of its existence, the South Korean Air Force—founded on Oct. 1, 1949, and known formally as the Republic of Korea Air Force (ROKAF)—has relied on its biggest ally, the United States, to supply it with warplanes, especially fighter planes. Indeed, according to the World Directory of Modern Military Aircraft, out of the 414 jet fighters in the ROKAF fleet, 354 of them are of U.S. origin. These include variants of the F-5 Tiger II, the F-16 Fighting Falcon, the F-15K Eagle, and the F-35A Lightning II.
However, slowly but surely the ROKAF has started venturing into the realm of homegrown fighters. The trend started with the fourth-generation KAI T-50/FA-50 Golden Eagle, which made its official operational debut in February 2005. Now South Korea’s defense aerospace industry is going one step further by building a fifth-generation stealth fighter—or at the very least, a warbird that straddles the line between 4.5 and the true fifth generation: the KAI KF-21 Boromae (“Fighting Hawk”).
KAI KF-21 Boromae Initial History and Premise
The Boromae is manufactured by Korea Aerospace Industries, Ltd. (KAI), which is headquartered in the city of Sacheon-si in South Korea’s Gyeongsangnam-do province. The Fighting Hawk first began development as part of the Korean Fighter eXperimental (KF-X) medium-class fighter project, which was first announced by then-South Korean President Kim Dae-jung in March 2001.
Although KAI and the Korean Agency for Defense Development are the lead entities on the project, the KF-21 isn’t an entirely domestic venture. International partners include Indonesia’s PTDI (now Indonesia Aerospace), Eurofighter Typhoon Limited, and Lockheed Martin. What’s more, the warbird incorporates parts from a hodgepodge of Western suppliers, such as General Electric Aerospace for the engine; Texstars for the canopy design; Martin-Baker for the ejection seat; as well as Cobham, Héroux-Devtek, and Leonardo.
The KF-21 made its maiden flight on July 19, 2022, 15 months after the first prototype was officially unveiled. A total of six prototype airframes have reportedly been built thus far.
KF-21 Technical Specifications and Vital Stats
Crew: 1 or 2
Fuselage Length: 16.9 m (55 ft 4 in)
Height: 4.7 m (15 ft 4 in)
Wingspan: 11.2 m (36 ft 7 in)
Empty Weight: 11,800 kg (26,015 lb.)
Max Takeoff Weight: 25,600 kg (56,400 lb.)
Powerplant: 2 × GE Aerospace F414-GE-400K turbofans, generating up to 97.1 kilonewtons (22,000 pounds-force) of thrust
Max Airspeed: Mach 1.81
Ferry Range: 2,900 km (1,800 miles)
Combat Range: 1,000 km (620 miles)
Armament:
Guns: 1× 20 mm M61A2 Vulcan Gatling gun
Missiles: Air-to-air missiles such as the AIM-120 ARMAAM (“Slammer”); air-to-surface missiles such as the AGM-65 Maverick; anti-ship missiles such as the Taurus KEPD 350
Bombs: Cluster bombs such as the CBU-97 Sensor Fuzed Weapon; guided bombs such as the JDAM
More Details
Though not a bona fide, full-fledged stealth fighter, the KF-21—in addition to bearing at least a superficial cosmetic resemblance to the F-35—does incorporates some semi-stealthy features, such as a low-observable/low radar cross section shape, flush antennas, an S-Duct intake, and a flat fuselage.
Moreover, the next edition of the warbird, designated the KF-21EX, will become even stealthier thanks to internal weapon bays.
The Way Forward for the KF-21
There is no real operational history to report here, as the warbird hasn’t even made its official debut yet; that is projected for 2026.
However, the future for the Fighting Hawk looks very bright.
As noted in an article by Jung Suk-yee for Business Korea Magazine, “The Republic of Korea’s aerospace industry is making history in defense technology as it begins full-scale production of the KF-21 ‘Boramae’ fighter jet…The Defense Acquisition Program Administration and Korea Aerospace Industries (KAI), the primary developer, have formalized the KF-21’s production through two sequential contracts. Following the first contract for 20 units in June 2024, a second contract for an additional 20 units was finalized in June 2025, confirming the production of 40 Block I variants. These 40 aircraft are scheduled to be delivered to the Korean Air Force between 2027 and 2028. With the future production of 60 Block II variants, which are expected to feature internal weapons carriage and enhanced stealth capabilities, the project moves closer to achieving the final goal of securing 120 KF-21s by 2032.”
National Security Journal will continue to track the progress of the KF-21 and report on new details as they become available. Stay tuned, dear readers.
About the Author: Christian D. Orr, Defense Expert
Christian D. Orr is a Senior Defense Editor. He is a former Air Force Security Forces officer, Federal law enforcement officer, and private military contractor (with assignments worked in Iraq, the United Arab Emirates, Kosovo, Japan, Germany, and the Pentagon). Chris holds a B.A. in International Relations from the University of Southern California (USC) and an M.A. in Intelligence Studies (concentration in Terrorism Studies) from American Military University (AMU).
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