South Korea has rolled out the first mass-produced KF-21 Boramae fighter at Korea Aerospace Industries’ Sacheon facility, with President Lee Jae Myung attending the March 25, 2026, ceremony. The Republic of Korea Air Force received its first Block I aircraft in September. The KF-21 was developed with Indonesian backing as a cheaper, less-stealthy alternative to the F-35, which South Korea also operates. Powered by twin General Electric F414 turbofans, the 4.5-generation fighter flies at Mach 1.8, carries 17,000 pounds across ten hardpoints, and integrates a Hanwha Systems AESA radar and the MBDA Meteor missile. Seoul plans to field 120 KF-21s by 2032.
K-21: South Korea Has A ‘Mini’ F-35
KF-21. Image Credit: Creative Commons.
South Korea rolled out the first mass-produced KF-21 Boramae fighter jet on March 25 at Korea Aerospace Industries’ facility in Sacheon – the first production delivery milestone for the country’s own domestically developed fighter program. President Lee Jae Myung attended the ceremony, and South Korea’s presidential office said the aircraft is scheduled to be delivered to the Republic of Korea Air Force and deployed for operations in September.
The KF-21 is a milestone for South Korea; it is the country’s attempt to build and sustain an advanced combat aircraft industry at home, reducing long-term dependence on imported fighters and expanding its role as an arms exporter. Lee said at the ceremony that South Korea would invest in advanced aircraft technologies, including engines and raw materials, to strengthen the country’s high-tech aviation sector.
The fighter, developed by Korea Aerospace Industries with support from Indonesia, was specifically designed as a cheaper, less-stealthy version of the U.S.-built F-35, which South Korea also operates.
KF-21 Enters Production
The KF-21 first flew on July 19, 2022, from an air base in Sacheon, and was developed under a project partially backed by Indonesia.
That test flight was important, but the March 2026 rollout is the more significant operational milestone, as it shows the aircraft has moved from prototype testing to serial production.
Janes reported that the first production KF-21 was presented at KAI’s Sacheon facility in South Gyeongsang province on March 25, 2026, and that the aircraft carried the Republic of Korea Air Force tail number 26-001.
KF-21 Boramae Fighter KAI Image
KF-21 Fighter from South Korea. Image Credit: Creative Commons.
KF-21. Image Credit: Creative Commons.
The first KF-21 Block I production aircraft is expected to be delivered to the Republic of Korea Air Force in September 2026. South Korea is expected to receive 40 Block I aircraft in total.
The Block I aircraft are expected to focus mainly on air-to-air missions, while later aircraft are expected to add additional strike capacity. The KF-21 is considered a 4.5-generation fighter and will use a mix of indigenous and Western sensors and weapons, including the Korean GPS-guided bomb and the MBDA Meteor air-to-air missile.
Why South Korea Built the Boramae
South Korea developed the KF-21 to replace aging combat aircraft while reducing reliance on foreign suppliers.
The country has long operated U.S.-designed fighters, including the F-4 Phantom II, F-5 Tiger II, F-16, and F-35, but the KF-21 gives Seoul a domestic platform that can be upgraded and exported under South Korean control.
F-4G. Image Credit: Creative Commons.
F-4G Wild Weasel in Museum. Image Credit: National Security Journal/All Rights Reserved.
South Korea needs these aircraft because of the permanent military threat from North Korea, whose missile and nuclear programs have forced Seoul to invest heavily in air and missile defense, as well as strike capability and advanced aircraft.
The KF-21 is not intended to be a direct substitute for the F-35, but it does provide the Republic of Korea Air Force with a modern aircraft that can replace older jets and supplement the stealth aircraft already in service.
The aircraft’s design is also a compromise: it is not a full-fledged fifth-generation stealth fighter, as early versions do not carry weapons internally, unlike the F-35. Instead, it sits closer to a 4.5-generation fighter that combines reduced radar visibility and modern sensors with advanced weapons, carrying a lower development risk and likely lower cost.
The result is not a platform that can compete with the F-35, but one that can support South Korean operations on a budget.
What the KF-21 Can Do
The KF-21 was designed to occupy the space between older fourth-generation fighters like the F-16 and expensive stealth aircraft like the F-35.
The aircraft uses twin General Electric F414-GE-400K turbofan engines – the same engine family used by the Boeing F/A-18E/F Super Hornet – allowing it to reach speeds of roughly Mach 1.8 while carrying a payload of approximately 17,000 pounds across ten external hardpoints.
F-16A on USS Intrepid NSJ Image. Taken by Jack Buckby on 9/18/2025.
FlightGlobal reported that the fighter has a combat radius of around 620 miles and was specifically designed for high sortie generation and relatively low operating costs compared to full-stealth aircraft.
The aircraft also incorporates a domestically developed active electronically scanned array (AESA) radar from Hanwha Systems, along with infrared search-and-track capability, electronic warfare systems, and sensor fusion to improve targeting and survivability.
Unlike older Korean fighters, the KF-21 was built from the outset for network-centric warfare, enabling it to operate alongside F-35s, drones, missile defense systems, and other allied assets during high-intensity operations.
South Korea deliberately avoided building a pure stealth aircraft because doing so would have dramatically increased costs, development time, and technical risk.
Instead, the KF-21 was designed as a more affordable multirole fighter optimized for regional operations, exportability, and long-term upgrade potential.
South Korea ultimately plans to field around 120 KF-21 fighters by 2032.
Seoul appears committed to building its own long-term combat aviation industry, but whether it succeeds as an international exporter remains to be seen.
About the Author: Jack Buckby
Jack Buckby is a British researcher and analyst specializing in defense and national security, based in New York. His work focuses on military capability, procurement, and strategic competition, producing and editing analysis for policy and defense audiences. He brings extensive editorial experience, with a career output spanning over 1,000 articles at 19FortyFive and National Security Journal, and has previously authored books and papers on extremism and deradicalization.
