South Korea begins KF-21 Boramae fighter jet assembly marking shift in global defense market.

On May 20, 2025, during a formal ceremony at Korea Aerospace Industries’ (KAI) production facility in Sacheon, South Korea’s Defense Acquisition Program Administration (DAPA) announced that the country had begun final assembly of the first mass-produced KF-21 Boramae multirole fighter aircraft. The final assembly phase involves integrating the aircraft’s fuselage, wings, engine nacelles, tail structures, landing gear, flight control systems, engines, and avionics. Ground system testing will follow, preceding flight trials. According to DAPA, this marks a formal transition from component-level production to aircraft-level integration, signaling the near-completion of the first KF-21 production unit.
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The first prototype of South Korea's KF-21 Boramae fighter jet was completed in April 2021, and achieved its maiden flight on July 19, 2022. (Picture source: KAI)

The final assembly is taking place ten months after production activities began in July 2024, and the aircraft is scheduled to be delivered to the South Korean Air Force (ROKAF) in the second half of 2026, following acceptance testing. The KF-21 project originated in 2015 as a national initiative to replace South Korea’s aging F-4E Phantom II and F-5E/F Tiger II fighters, the former of which was retired in 2024. Development of the aircraft has proceeded over a period of ten years and six months, and its production involves the participation of over 600 domestic companies. The program has aimed for a localization rate of approximately 65%, with several systems, including the AESA radar and the mission/flight control computer, developed domestically. The aircraft is powered by two General Electric F414-GE-400K turbofan engines, each offering 57.8 kN of thrust (97.9 kN with afterburner). KAI began the low-rate initial production of 20 Block I aircraft following a contract signed with DAPA on June 25, 2024, valued at KRW 1.96 trillion ($1.41 billion), with the agreement also covering training and logistical support. Initial production included small-part machining, component manufacturing, and subassembly of the front, center, and rear fuselage sections before reaching the current stage. A second contract for another 20 aircraft is expected to be awarded in 2025.

The KF-21 Boramae is a twin-engine, 4.5-generation supersonic fighter designed to perform air superiority and precision strike roles. It has a maximum takeoff weight of approximately 25,600 kg, a ferry range of about 2,870 km, and a maximum speed of Mach 1.81 (2,220 km/h). It can carry up to 7,700 kg of payload. The aircraft incorporates several design elements similar to those of the F-22 Raptor, including canted twin tails and angular air intakes. It is also equipped with a conformal internal gun mounted above the left air intake, a feature similar to that found on the F-35A. While not categorized as a fifth-generation aircraft, the KF-21 includes some low-observable design aspects and is intended to serve as a cost-effective complement to South Korea’s existing fleet, which includes the U.S.-built F-35A. In December 2023, South Korea ordered 20 additional F-35As as part of the second phase of the F-X III procurement program. The ROKAF plans to acquire a total of 120 KF-21s by 2032.

Flight testing of the KF-21 began on July 19, 2022, at Sacheon Airport. The test campaign is being conducted using six prototypes, four single-seat and two twin-seat variants, with over 1,000 flights completed by the end of 2024 and a goal of reaching 2,000 test flights by 2026. These tests have included air-to-air missile launches and aerial refueling, including at night. The aircraft has been successfully integrated with the European-supplied Meteor beyond-visual-range air-to-air missile and the IRIS-T short-range missile. It is also planned to carry the Taurus KEPD 350 air-launched cruise missile. The AESA radar, a critical component of the aircraft’s fire control system, was tested on a modified Boeing 737-500. The flight control software, mission computer, and avionics systems were developed by South Korean firms, further contributing to the national industry base.

The KF-X/IF-X program was initiated in cooperation with Indonesia, which agreed in 2014 to contribute 20% of the total development cost, originally estimated at 7.5 trillion KRW ($6.3 billion). However, Indonesia delayed its financial contributions starting in 2018 and repeatedly sought to renegotiate its share. In 2021, it resumed payments, but concerns persisted. In May 2024, Indonesia formally approached South Korea to revise its participation terms again, and by August, South Korea agreed to lower Indonesia’s contribution to 600 billion KRW from the original 1.6 trillion KRW. In February 2025, the two governments reaffirmed their cooperation. However, questions remain over Indonesia’s commitment to procure 50 KF-21s, especially following media reports that it is also evaluating the Turkish Aerospace Kaan fighter. In 2024, two Indonesian engineers were found attempting to remove unauthorized flash drives from KAI’s facilities. A joint investigation by DAPA, the National Intelligence Service, and the Defense Counterintelligence Command concluded that no classified KF-21 data were compromised.

South Korea has expressed interest in offering the aircraft to the Philippines and Peru, but both countries are also considering other platforms. In Peru, media reports indicate a preference for more established aircraft such as the Dassault Rafale, Lockheed Martin F-16, and Saab Gripen. In April 2025, DAPA publicly urged Peru to ensure a fair and competitive selection process. In the Philippines, the U.S. F-16 Block 70 appears to have an advantage, particularly after a visit by U.S. Secretary of Defense Pete Hegseth. South Korea has also signed a cooperation agreement with the United Arab Emirates, allowing UAE Air Force personnel to observe KF-21 operations once the aircraft enters service. This agreement, signed in April 2025, formalizes bilateral cooperation in areas such as training and evaluation of the fighter and includes provisions for UAE participation in future exercises involving the KF-21.

The final assembly of the first production KF-21 is viewed by DAPA as a validation of the system development phase and a clear indicator of progress in the domestic fighter program. DAPA also emphasized that the milestone will positively affect ongoing and future export discussions by demonstrating tangible production capability. According to Jeong Gyu-heon, head of DAPA’s Future Power Division, the milestone was achieved through coordination between government agencies, defense companies, and development partners. Officials have reiterated that seamless cooperation across institutional and industrial stakeholders is essential for the successful delivery of the program and its contributions to national defense and the aerospace sector. The final aircraft in the first production batch is scheduled for delivery by 2028.