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KAI KF-21 Boramae

South Korean fighter aircraft From Wikipedia, the free encyclopedia

KAI KF-21 Boramae
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The KAI KF-21 Boramae (Korean: KF-21 보라매; KF-21 Fighting Hawk; formerly known as KF-X; commonly referred to as the KF-21) is a South Korean-led fighter aircraft development program with the initial goal of producing multirole fighters for the Republic of Korea Air Force (ROKAF).[1][4] The airframe uses stealth technology but carries weapons externally,[5][6] and features such as internal bays will be introduced later with KF-21EX program.[7][8] The KAI KF-X is South Korea's second domestic fighter jet development program, following the FA-50.[9]

Quick facts KF-21 Boramae, General information ...

The program is led by the South Korean government, which holds 60% of the shares. The remaining 20% is held by the manufacturer Korea Aerospace Industries (KAI)[9], with Indonesia holding the final 20% stake.[10] Later, in August 2024, Indonesia's stake was reduced to 7.5% due to Indonesian government request.[11][12]

In April 2021, the first prototype was completed and unveiled during a rollout ceremony at the headquarters of KAI at Sacheon Airport.[13] It was named the Boramae.[note 1][14][15][16] The first test flight was on 19 July 2022. The serial production started in July 2024. 40 aircraft are planned to be delivered by 2028, with Republic of Korea Air Force expecting to deploy 120 of the aircraft by 2032.[15] It will also be available for export.[17] The Republic of Korea Air Force will begin replacing its F-4D/E Phantom II and F-5E/F Tiger II jets with KF-21s. Later, F-16 Fighting Falcon and F-15EX Eagle IIs will also be replaced.[18][19]

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Background

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The KF-X advanced multirole jet fighter project, intended to produce modern warplanes to replace South Korea's aging F-4D/E Phantom II and F-5E/F Tiger II aircraft, was first announced in March 2001 by South Korean President Kim Dae-jung at a graduation ceremony of the Korea Air Force Academy.[20] In 2002, research and development (R&D) requirements were determined by the Joint Chiefs of Staff.[21]: 18  The project was felt to be extremely ambitious, with the Korea Institute for Defense Analyses (KIDA, a defense ministry think tank) doubtful of the country's ability to complete the complicated project.[22]

The development phase had numerous delays and postponements and its economic cost was debated, but the project received renewed interest following a 2008 feasibility study and attacks by North Korea in 2010.[22][23] Although the project carried risks and the expected per-unit cost would be significantly higher than purchasing from foreign manufacturers, the development of the domestic defense industry was deemed to be of national importance and was expected to have a ripple effect on high-tech industries.[21]: 22, 37 

In Indonesia, the KF-X development program is referred to as the IF-X program.[22][24] The Jakarta Globe reported that the completed aircraft would have received the designation F-33.[22] On 15 July 2010, a partnership was made with Indonesia, which would provide 20% of the funding for the KF-X project, cooperate with technological development through state-owned Indonesian Aerospace, and purchase 50 of the approximately 150–200 planned aircraft.[20]

Turkey had been considering joining with a 20% share, but wanted more control than South Korea had offered. The South Korean government committed to 60% of the cost.[22] The remaining 20% was provided by domestic and foreign companies.[21]: 18  The contract formed a plan for delivery of the aircraft to begin in 2026.[25]

In July 2022, the Polish Armaments Agency said it is closely watching the development of the KF-21 Boramae, potentially paving a way for the purchase of the future Block 2 version of the fighter jet for the Polish Air Force.[26] Since the beginning of the Russian invasion of Ukraine on 24 February 2022, Poland has boosted its military expenditures. On 31 January 2020, Poland ordered 32 F-35A.

The Philippine Air Force and the Peruvian Air Force have expressed interest in the KF-21.[27][28]

In May 2023, the Defense Acquisition Program Administration said that the KF-21 had passed the provisional combat suitability evaluation, to begin the initial mass production process in 2024.[29]

Starting with the first prototype on 19 July 2022, six prototypes flew maiden flights until June 2023. The six prototypes will be tested for performance verification.[30]

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Design and development

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KF-21 sixth prototype demonstrating basic fighter maneuvers in Seoul ADEX 2023

The initial goal for the program was to develop a single-seat twin-engine multirole fighter with stealth capabilities exceeding the Dassault Rafale, Eurofighter Typhoon, F-16 Fighting Falcon but less than those of the Lockheed Martin F-35 Lightning II.[22] The Weapon Systems Concept Development and Application Research Center of Konkuk University advised that the KF-X should be superior to the F-16 Fighting Falcon, with 50% greater combat range, 34% longer airframe lifespan, better avionics, active electronically scanned array (AESA) radar, more-effective electronic warfare, and data link capabilities. Their recommendations specified approximately 50,000 pounds-force (220,000 N) of thrust from two engines, supersonic interception and cruising capabilities, and multi-role capabilities.[31] The project requirements were later downgraded by the Republic of Korea Air Force (ROKAF) to a 4.5 generation fighter with limited stealth capabilities.[22]

South Korea possessed 65% of the necessary technology to produce the KF-X,[32][33] and sought cooperation from other countries.[31] To facilitate technology transfer, the Agency for Defense Development (ADD) proposed two primary concepts for the KF-X: C103, which resembled the F-35,[22][34] and C203, which resembled European fighters with forward canards. The design chosen would depend upon whether a development deal was reached with the US or European partners.[22]

The C501 (a.k.a. KFX-E) was a third design,[22] proposed by KAI[34] and supported by the Defense Acquisition Program Administration (DAPA),[35] which attempted to reduce costs with a smaller, single-engine fighter, but it had inferior performance to the F-16 and was unsuitable for the large airspace of Indonesia.[22] ROKAF preferred the benefits of a twin-engine design, with better combat performance and safety, and a larger airframe with room for upgrades. These upgrades could lead to a future reclassification as a fifth-generation fighter, while the C501 was closer to fourth generation.[35][36]

When the development team started designing the KFX in December 2015, research and design was conducted based on the C103 configuration. Upon receiving the basic drawings of the C103, C104, and C105 from ADD, the development team built an experimental model of the C105 and began a wind tunnel experiment on the newly designed C107, which increased the size of the aircraft and increased the max takeoff weight. After about 2 years of various wind tunnel experiments, in 2018, the C109 proposed by ADD and KAI was decided to be the prototype design of KFX.[37]

In May 2016, the U.S. government and Lockheed Martin tentatively agreed to transfer 21 technologies to KAI under the terms of offset trade, which is part of a contract for South Korea to introduce the F-35A.[38] Later, The US government blocked the transfer of four vital technologies: AESA radar, infrared search and track (IRST), electro-optical targeting pod (EO TGP), and radio frequency jammer (RF jammer) technology. South Korea was required to develop these technologies domestically.[22][39] A 2015 audit estimated that 87% of technologies for the project had been secured.[21]: 23  The preliminary design was finalized in June 2018.[40] In September 2019, a critical design review examined 390 technical data sets and confirmed that the KF-X was adequate to ROKAF's requirements.[41][42][43]

Modular design and evolutionary approach

The KF-21 program's core philosophy centers on a spiral development model, where the aircraft is introduced in a series of progressively more capable versions, or blocks. This modular approach allows for incremental improvements, with each block introducing new capabilities and technologies. The initial focus was on developing a highly capable 4.5-generation fighter jet with scalability to be upgraded to a true 5th-generation aircraft in later iterations.[44][45][46] It was intended to both fulfill the Republic of Korea Air Force's urgent need to retire its F-4 Phantom II and F-5 Tiger II jets and to secure opportunities for future upgrades.[18]

The initial production version, the KF-21 Block I, is a 4.5-generation fighter with semi-stealth features, lacking an internal weapons bay and carrying its ordnance on 10 external hardpoints. The planned Block II variant will be a multi-role aircraft, integrated with a wider range of air-to-ground and anti-ship weapons. The ultimate goal is the Block III, a true 5th-generation stealth fighter, which will feature an internal weapons bay and improved sensors. KAI's strategy is that the Block III can be introduced when the technology and budget are ready, building upon the mature airframe and systems of the earlier blocks.[44][45]

This evolutionary path reduces the initial development risk and shortens the time to fielding an operational aircraft.[46] By focusing on a more attainable 4.5-generation platform first, KAI was able to start serial production and begin squadron service just five years after the first prototype's maiden flight. This approach also makes the program more financially manageable and allows for a "fly before you buy" model for potential export customers.[46][44][45]

Dual-path approach

The KF-21 program, led by Korea Aerospace Industries (KAI) and the Agency for Defense Development (ADD), prioritizes the indigenization of key technologies where feasible. The strategic rationale behind the KF-21 Boramae's development is to first create a highly capable and cost-effective 4.5 generation fighter by combining domestic technological advancement with proven international expertise. This dual-path approach allows South Korea to avoid the significant time and cost of developing every component from scratch, while simultaneously building its own defense industrial base. Besides, such an approach can also provide future users with further credibility on capability and reliability of a newly developed aircraft.[46] Most importantly, this strategic approach allowed the KF-21's unit cost to be 30-40% cheaper than that of the Rafale and Eurofighter.[47]

By focusing on the in-house development of critical, sensitive technologies like the AESA radar and electronic warfare systems, the program enhances national self-reliance and bypasses potential arms-trading restrictions.[48][49] For other components, such as engines and flight control systems, KAI contracts with experienced international partners to ensure reliability and performance, thereby meeting a challenging project timeline and budget.[50] This balanced strategy maximizes the value of local investment by concentrating on what is strategically important to develop domestically, while leveraging foreign expertise to produce a complete, high-performance aircraft.

While core technologies such as the AESA radar, EO TGP, IRST, and RF jammer were developed locally, foreign companies were consulted for counter-testing and technical advice to ensure the reliability of these systems and to navigate arms-trading restrictions.[48][49] In August 2016, Hanwha Systems commenced full-scale development of the AESA radar under the leadership of the Agency for Defense Development.[51][52] In 2020, Hanwha Systems successfully produced a prototype[53] and Elta Systems helped to test the performance of the prototype hardware of the AESA radar.[48][54] Saab provided technical advice to LIG Nex1, which develops Multi Function Radar (MFR) software for AESA radars.[55][49] On August 5, 2025, Hanwha Systems unveils the first mass-produced AESA radar.[53] The infrared search and track (IRST) is based on the processor unit (PU) designed by Hanwha Systems and a Leonardo sensor head unit (SHU) called the SkyWard-K with a Korean software.[53][56][57][58][59] The electro-optical targeting pod (EO TGP), and integrated electronic warfare suite (EW Suite) was developed by domestic companies.[53] Specifically, the RF jammer was developed by LIG Nex1.[60][61][62]

For the engine, Hanwha Aerospace signed an agreement with General Electric to manufacture General Electric F414 engines for KF-X aircraft. According to the contract, Hanwha is to manufacture key parts, locally assemble the engines, and oversee the installation of the engine on the aircraft. The company will support flight testing and build an extensive support system for the aircraft's operations.[50][63][64]

For some less critical components that can be sourced more cost-effectively than developing them domestically, KAI and ADD strategically partnered with numerous international companies. For instance, Texstars was contracted to provide birdstrike-resistant canopy and windshield transparencies.[65][66] Triumph Group supplies the airframe mounted accessory drives (AMADs), which transfer engine power to other systems.[67][68] Other notable collaborations include Aeronautical Systems (CESA) for the emergency braking system[69][70], United Technologies for the environmental control system[71][72], and Martin-Baker for the Mk18 ejection seat.[73][74] Cobham provides missile ejection launchers, external fuel tanks, and oxygen systems[75], while Meggitt is responsible for the wheel braking system and internal sensors.[76] standby flight displays, and internal sensors including a fire detection system.[77][78][79] The program also benefits from contributions by Elbit Systems for terrain-following systems[80][81] and Curtiss-Wright, which supplies the flight test instrumentation system for data acquisition.[82][83] This international cooperation for minor systems highlights a pragmatic approach to the KF-21's development, ensuring the aircraft maintains lower unit cost and is equipped with reliable, proven components.

The strategic approach taken for the KF-21 program, which involves combining local development of core technologies with some international cooperation for minor components, has been noted by analysts as a practical and effective way to manage a complex project. While other competing programs, such as Turkey's Kaan and India's AMCA, have pursued a more ambitious, fully indigenous development path, the KF-21's model has been credited with achieving its development goals in a relatively efficient manner. The KF-21 program has been recognized for its adherence to its original timeline and budget, a notable accomplishment in a field where major defense programs frequently encounter delays and cost overruns.[46]

The local production rate for domestic components of KF-21 Block I has reportedly exceeded 65%.[19] KAI plans to further increase the domestic components as it develops future blocks, when it is expected to domestically produce reliable parts cost-effectively.[84]

Differences between design configurations

A subsonic wind tunnel test of the scale model of KF-X C105 at the Korea Aerospace Research Institute
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Prototypes

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The fourth prototype during a full-scale airframe environmental testing, 2024

In February 2019, KAI began production work on the KF-X prototype, with six expected to be completed in 2021. These will undergo four years of trials, and complete the development process by mid-2026.[88] The first prototype was publicly rolled out on 9 April 2021. In addition to the six aircraft for airborne tests, two will be made for ground tests.[89] On 19 July 2022, the first test flight occurred at Sacheon Airbase for 33 minutes.[90][91] Six flying prototypes, including two two-seat versions, will conduct 2,200 flights until mass production begins in 2026. [90][91]

The second KF-21 prototype flew in November 2022 and a third in January 2023, achieving the aircraft's first supersonic flight in January. The first two-seat KF-21 prototype flew in February 2023. The two-seater's primary role will initially be type conversion. DAPA is considering other operational missions that would be more suited to a two-seat platform including electronic warfare.[92]

Budget

R&D expenditures

A 2015 government audit placed the development cost of the project at ₩8.8 trillion[21]: 18  (equivalent to ₩9.06 trillion or US$8.01 billion in 2017)[93]. In an agreement signed at the end of 2015, Indonesia agreed to provide 20% of the development costs.[25] KAI would provide an additional 20%,[citation needed] and the Korean government would support the remainder.[25][better source needed]

More information Calendar Year, Expenditures on R&D ...
More information Calendar Year, Expenditures on R&D ...

Indonesian investment

See also: KAI KF-21 Boramae § Indonesian renegotiation

In July 2010, the Indonesian government agreed to fund 20% of the KF-X project cost in return for prototype 005 (designated IF-X), system development participation, technical data, and production sharing.[98][38] In August 2011, a joint research center was opened in Daejeon, South Korea.[99][100] The second agreement between Indonesia and Korea was a work assignment agreement between KAI and Indonesia's state-owned aerospace manufacturer PT Dirgantara (PTDI). As per this agreement, PTDI sent 100 engineers to South Korea to take part in the structural design of the KF-21, to play a role in its development over time.[101]

In November 2017, Indonesia, through state-owned Indonesia Aerospace, failed to pay its share of the latest round of development costs, prompting criticism from South Korea.[22][102] As of 2019, Indonesia was renegotiating its involvement in the program.[40] FlightGlobal reported in July 2019 that Indonesia was exploring payment in Indonesia-produced armaments instead of cash.[43] By July 2019, Indonesia was approximately ₩300 billion in arrears.[103]

Yonhap reported in October 2019 that, according to DAPA Korea, there were 114 Indonesian engineers participating during the peak of the KF-21 design phase in July 2019 and the development was ready to go to the prototyping stage after it met all of the requirements in September 2019.[104]

According to a September 2023 report from Yonhap, the South Korean state news agency, Indonesia had paid only US$208 million since 2016 on the research and development stage[105] Another report stated that Indonesia paid US$205 million for research and development and owed about US$420 million.[106] In December 2020, a report showed that Indonesia was likely to pull out of the project.[107] Another stated that South Korea and Indonesia planned to move forward on the KFX/IFX project.[108]

In August 2021, Indonesia reaffirmed its interest in the KF-21 program, with Indonesian engineers returning to South Korea to continue their work.[109] Further agreement on the costs has been reached between the two countries.[110][111]

According to reports in May 2022, the issue of Indonesia's unpaid US$4.2 million in development costs had not been resolved. In November 2021, Indonesia and South Korea agreed to draw up a new sharing agreement for development costs by March 2022, but it had not been implemented so far.[112] In November 2022, reportedly Indonesia has resumed payment for its share of the cost for a joint fighter development project.[113]

In September 2023 it was reported that Indonesia did not make its payments, and South Korea had signed a memorandum of understanding with the United Arab Emirates (UAE), that the UAE would buy Indonesia's KF-21 shares and be part of the KF-21 program as a partner.[114] The rumors about the United Arab Emirates joining the KF-21 program was denied by DAPA Korea based on Korean government-owned media, Yonhap.[105] Indonesian Defense Ministry Technology Director Air Vice Marshal Dedy Laksmono confirmed to the press on 29 October 2023 that the budget for 2024 cost share payment had been set aside at 1.25 trillion rupiah (US$80 million).[115]

On 21 February 2024, on the sidelines of the G20 meeting in Rio de Janeiro, Brazil, Indonesia foreign minister Retno Marsudi and her counterpart South Korean foreign minister, Cho Tae-Yul, discussed the KF-21/IFX program, and both parties once again reaffirmed their commitment to continue the joint development program between the two countries.[116]

The Korea Aerospace CEO said in the Korean media that Indonesia entering the program is pretty significant for KF-21 development and the program could have been stalled if there was no continued Indonesia participation.[117]

On 16 August 2024, the 163rd Defense Acquisition Program Promotion Committee readjusted the development contributions Indonesia was supposed to pay from ₩1.6 trillion to ₩600 billion, and Indonesia's stake was reduced to 7.5% as the shortfall was decided to be covered by the Korean government's additional budget.[11]

Polish interest

At the Polish-Korean Defense Industry Cooperation Conference in Warsaw in November 2022, Sebastian Chwałek, chairman of Polish Armaments Group (PGZ), a state-owned defense company, expressed his desire to participate in the KF-21 project.[118]

According to a South Korean government official, in May 2023, during a visit to Korea in mid-April 2023, Sebastian Chwałek, chairman of the PGZ, expressed Poland's desire to participate in the KF-21 project. Specifically, the Polish government wanted to join the project as a development partner in 2026, after the KF-21 Block-1 is developed and when Block-2 begins development. It is reported that the Polish government is discussing the possibility of acquiring Indonesia's stake in the program by paying the ₩800 billion in overdue contribution funds that the Indonesian government has failed to pay. PGZ reportedly plans to deliver a letter of intent to participate in development partners to the South Korean government soon through the Polish government. The South Korean Defense Acquisition Program Administration said it will begin a full-fledged review once it receives a letter of intent from the Polish government.[119]

Testing achievements

In January 2022, the final assembly of the KF-21 occurred.[120]

In March 2022, ground testing was conducted for the AESA radar. The AESA radar of the KF-21 is equipped with about 1,000 transmit/receive modules and electronically steers the radar beam by adjusting the phase of the radio waves.[121]

In April 2022, the AESA radar began its domestic flight tests. By the first half of 2023, all developed functional and performance requirements of the AESA radar were verified through flight tests. Various flight scenarios and repeated tests improved the completeness and reliability of the AESA radar. In South Africa, a civilian aircraft (Boeing 737-500) was modified to create a test aircraft (FTB: Flying Test Bed) equipped with the AESA radar. From November to December 2021, a total of 10 sorties were conducted to test the basic functions and performance of the radar, including its most critical performance, maximum detection range.[122][123]

On 6 July 2022, the first prototype of the KF-21 conducted a ramp taxi test in preparation for its maiden flight.[124][125][126][127]

On 7 July 2022, the final engine run test.[128] and a high speed taxi test was conducted in preparation for its maiden flight.[129]

On 19 July 2022, the KF-21 successfully completed its maiden flight. The KF-21 took off at 3:40 PM and landed at 4:13 PM, marking a successful 33-minute first flight. It will undergo approximately 2,000 flight tests in the future to verify various performance aspects and weapons compatibility.[130][131][132]

On 28 September 2022, the ROKAF released a video demonstrating the KF-21's landing gear operation during flight, addressing public curiosity about the mechanics of the landing gears and caps.[133]

On 10 November 2022, the second prototype took off from Sacheon Air Base in South Gyeongsang Province, tested its flight performance for 35 minutes, and landed safely.[134]

On 3 January 2023, the third prototype successfully completed its first test flight. The third prototype took off from the 3rd Training Wing in Sacheon, South Gyeongsang Province at 1:01 PM and landed at 1:38 PM. The first test flight recorded a maximum speed of 370 km/h and a maximum altitude of 4,600 meters, which is similar to the levels achieved by the first and second prototypes. The third prototype is equipped with speed and structural load expansion measurement systems. It is expected to facilitate smoother speed and structural load expansion tests, which constitute a significant portion of the KF-21 system development flight tests.[135][136]

On 17 January 2023, the KF-21 successfully achieved its first supersonic flight. The KF-21 first prototype took off from the ROKAF's 3rd Training Wing and broke the sound barrier (Mach 1.0, approximately 1,224 km/h) for the first time while flying at an altitude of about 40,000 feet over the South Sea.[137]

On 20 February 2023, DAPA announced that the fourth prototype of the KF-21 successfully completed its maiden flight, taking off from the 3rd Training Wing in Sacheon at 11:19 AM and landing at 11:53 AM after a 34-minute flight. The fourth prototype is a two-seat aircraft with seats arranged in tandem, accommodating two pilots. The two-seat KF-21 will primarily be used for training new pilots (prototype composition: 4 single-seat (prototypes 1, 2, 3, 5), 2 two-seat (prototypes 4, 6)). Despite being a two-seat aircraft, only one pilot flew the fourth prototype for this initial flight to verify early flight stability. Until the completion of system development in June 2026, the fourth prototype will undergo various flight tests to assess the impact of design differences on the aircraft, perform AESA radar avionics tests, and more. The livery of the fourth prototype features an image of four aircraft simultaneously ascending into the sky on the vertical tail, similar to the third prototype, but with yellow-colored ascending aircraft. With the fifth and sixth prototypes starting flight tests in the first half of 2023, all six prototypes will continue expanding the flight envelope and verifying aircraft performance through continuous flight tests.[138]

On 9 March 2023, KF-21 prototypes 3 and 4 successfully completed a night flight test and landed safely. During this test flight, the proper functioning of both internal and external lighting systems on the aircraft was verified in a low-light environment. The lighting on the aircraft plays an important role in night flights, including collision avoidance and identification of instruments for the pilot. With this successful test, it is expected that the KF-21 will be capable of performing nighttime missions.[139]

On 28 March 2023, DAPA announced, 'The KF-21 successfully conducted air-to-air weapon separation tests and aerial gun firing tests over the South Sea, taking off from the Air Force's 3rd Training Wing in Sacheon.' The second KF-21 prototype conducted weapon separation tests with Meteor medium-range air-to-air missile test round, while the third prototype performed aerial gun firing tests with around 100 rounds. These tests aimed to verify the safety by checking changes in the aircraft's structure, engine, and aerodynamic characteristics that can occur when weapons are separated or guns are fired from the fighter jet, and to confirm the normal operation of avionics systems related to weapon operation. Since its maiden flight in July 2022, the KF-21 has conducted approximately 150 flight tests, successfully verifying its supersonic flight capabilities and the performance of advanced avionics including the AESA radar.[140]

On 4 April 2023, the KF-21 successfully conducted a weapon separation test with AIM-2000 short-range air-to-air missile test round. This test aimed to verify the safety by checking for changes in the aircraft's structure, engine, and aerodynamic characteristics that can occur when weapons are separated from the fighter jet, and to confirm the normal operation of avionics systems related to weapon operation.[141]

On 16 May 2023, DAPA announced that the fifth prototype successfully completed its maiden flight, taking off from the 3rd Training Wing in Sacheon and flying over the South Sea. With the successful maiden flight of the fifth prototype, all four single-seat KF-21 prototypes have now completed their first flights. The fifth prototype will primarily conduct avionics performance verification tests, including those for the AESA radar, and is scheduled to undergo aerial refueling tests in the second half of 2023.[142]

On 23 May 2023, DAPA revealed the site of the mounting demonstration for the Meteor medium-range air-to-air missile and the AIM-2000 short-range air-to-air missile.[143]

On May 16, 2023, DAPA announced that the KF-21 Boramae had been declared "provisionally suitable for combat." After over two decades of development, including more than 200 flight tests, the KF-21 has proven its capabilities, such as supersonic and night flight, and has successfully tested its Active Electronically Scanned Array (AESA) radar and AIM-2000 air-to-air missile separation.[144]

On 28 June, DAPA announced that the sixth prototype successfully completed its maiden flight, taking off from the 3rd Training Wing in Sacheon, and flying for 33 minutes from 3:49 PM to 4:22 PM. With the successful maiden flight of the sixth prototype, all six KF-21 flight test prototypes have now completed their first flights. This milestone comes 11 months after the first prototype's successful flight on 19 July 2022.[145]

On 12 October 2023, the KF-21 prototypes 3 and 4 conducted a formation flight.[146]

On 20 October 2023, at the Seoul ADEX, the KF-21 showcased its technological capabilities during a five-minute demonstration, performing maneuvers such as horizontal sharp turns and inverted flights. This was the first time the aircraft's flight performance was revealed to the public.[147]

On 12 January 2024, the KF-21 second prototype successfully conducted a high angle of attack (AOA) flight stability test. The aircraft maintained a maximum pitch angle of approximately 70 degrees, flew to an altitude of over 38,000 feet, and then successfully returned to a stable flight condition after reaching a low-speed state (below approximately 20 KCAS).[148]

On 19 March 2024, DAPA announced that the fifth prototype (single-seat) successfully completed an aerial refueling flight over the South Sea after taking off from the Air Force's 3rd Training Wing in Sacheon. This achievement has secured the KF-21's long-range operational capability.[149][150]

On 22 April 2024, the KF-21 fourth prototype conducted a "full-scale environmental test" at the Agency for Defense Development's Haemi Test Center. This test verifies the aircraft's normal operation in extreme environments (low temperature, heavy rain, and icing). The test simulated extreme rain and icing conditions on the ground to check the KF-21's waterproof and anti-icing performance. The test results were successful.[151]

In May 2024, the KF-21 surpassed Mach 1.8, the highest speed achieved by a domestically produced fighter jet, during a test flight.[152]

On 8 May 2024, a KF-21 equipped with a Meteor missile successfully completed its test from Sacheon Airport. The same day, it also aced an AIM-2000 missile test, tracking a drone 87 km away and passing within 1 meter using AESA radar.[153] Later that month, a KF-21 successfully fired an IRIS-T missile for the first time, following earlier tests with an unguided dummy missile of the same type in 2023.[154]

On 24 October 2024, Prototype 6 of the KF-21 Boramae demonstrated exceptional stability and agility at Sacheon Airshow 2024, performing advanced maneuvers with precision.

On 28 November 2024, KAI's KF-21 Boramae achieved a milestone of 1,000 accident-free flight sorties, showcasing its outstanding safety and reliability.

On 19 February 2025, Air Force Chief of Staff Lee Young-su participated in a KF-21 Boramae test flight at Sacheon Air Base, becoming the first non-test pilot to fly aboard the aircraft. Gen. Lee flew at an altitude of approximately 4,500 meters over the southern coast at a speed exceeding 1,000 km/h, assessing the KF-21's stable aerial operational capabilities. Additionally, he flew alongside a KF-16 to verify its tactical interoperability with other aircraft.

On 8 April 2025, the KF-21 Boramae successfully conducted its first nighttime aerial refueling trial with the KC-330 tanker. Performed using the fourth prototype, the test was completed on the first attempt under low-visibility conditions, demonstrating the aircraft’s all-weather and long-range operational capabilities.

Serial production

In June 2024, 20 units of KF-21 Block I ordered for a value of USD $1.41 billion.[155]

In July 2024, the serial production of the 20 KF-21 Block I started.[156]

On May 20, 2025, the Defense Acquisition Program Administration (DAPA) marked the start of final assembly for the first mass-produced KF-21 Boramae fighter jet with a special ceremony.[157]

In June 2025, additional 20 units of KF-21 Block I ordered with the delivery of 40 units begins in September 2026 and completes by 2028.[158]

On August 5, 2025, Hanwha Systems rolls out the first mass-produced AESA radar.[53] The resulting domestically produced radar, the APY-016K is equipped with approximately 1,000 transmit-receive modules, enabling it to detect targets from 150-200 km away and track about 20 targets simultaneously, allowing the KF-21 to engage multiple enemies effectively.[53]

On August 8, 2025, DAPA reported that the KF-21 Block II version, which includes air-to-ground (A2G) capabilities, is now anticipated to be ready by early 2027. This acceleration of the development schedule by more than 1.5 years demonstrates that the project has exceeded its initial expectations.[159]

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Controversies

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Perspective

Foreign bribery allegations

In October 2009, a retired ROKAF general was arrested for leaking classified documents to Saab. The general was alleged to have been given a bribe of several hundred thousand dollars for copies of a number of secret documents that he had photographed. Saab officials denied any involvement.[160][161][162]

The Defense Security Command (DSC) found evidence that another foreign defense firm had also bribed a member of the Security Management Institute (SMI). President Lee Myung-bak believed that such corruption resulted in a 20% increase in the defense budget.[163][needs update]

Opposition

In 2017, the Korean defense think tank KIDA told a public meeting that South Korea is not technologically equipped to develop the KF-X aircraft, that the project is economically unviable and that the KF-X would not be a successful export product. It also questioned the ADD cost estimates.[164] DAPA's estimated ₩6 trillion development cost was criticized by some analysts, who said the project could cost up to ₩8.5 trillion.[165][166]

Defense researcher Lee Juhyeong held a seminar on the program, stating that the KF-X development would cost more than ₩10 trillion (US$9.2 billion) and could cost more than twice as much as an imported aircraft over the life of the program.[167]

Critics noted that the KF-X would cost up to twice as much as a top-end F-16 model and that Japan had encountered a similar situation with its Mitsubishi F-2.[168]

EADS funding pullout

In May 2013, EADS (European Aeronautic Defence and Space Company), the defense subsidiary of Airbus, offered a US$2 billion investment into the KF-X program, if South Korea selected its Eurofighter Typhoon for the F-X Phase 3 fighter procurement program.[169] The US F-35A was selected instead. EADS repeated its investment offer, for a split-buy of 40 Eurofighters and 20 F-35As.[170] In September 2017, South Korea confirmed purchase of 40 F-35 fighter jets, causing EADS to withdraw its offer.[171]

Postponements and delays

The KF-X project had a history of delays and postponements since its announcement in 2001. Foreign partners were sought to share costs and guarantee purchases, and several failed attempts were made to entice Sweden, Turkey, and the United States to join the project. Design concepts and requirements frequently changed while trying to appeal to prospective partners. In March 2013, following the election of President Park Geun-hye, South Korea postponed the project for 18 months, due to financial issues.[165][166]

In February 2017, Indonesian Vice Minister of Foreign Affairs Abdurrahman Mohammad Fachir said that the KF-X project was further delayed because the US government had refused export licenses for four key F-35 technologies. This disapproval was reaffirmed in October 2015 talks, though the US military stated that there was an agreement to form an interagency working group on such issues and that the US Secretary of Defense would "think of ways for joint cooperation" with technology for KF-X.[172][173][174]

In November 2017, state-owned Indonesia Aerospace was overdue in its funding payment, which National Assembly Defense Committee member Kim Jong-Dae said would further delay, or suspend the project.[175][176] Kim said that the Indonesian government had disclosed its difficulty in paying and did not include the payment in its budget. DAPA stated that it was in talks with Indonesia regarding the payment, which would be discussed at a summit between leaders of the countries.[102][needs update] Indonesia stated that it was an administrative error, as it was falsely thought that the payment would be made from the "side defense budget". Parliamentary approval was required to correct the error,[177] and the payment was delivered along with a statement of hope that the program would continue without further delinquencies.[178]

Indonesian renegotiation

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KF-21 scale model in Indonesian Air Force markings at Indo Defence 2024

On 1 May 2018, it was reported that Indonesia had complaints concerning the contract rules surrounding technical benefits and export licensing. Indonesian state media announced that the defense ministry would renegotiate the joint development program in an attempt to gain a larger share of local production, as well as export rights. The Indonesian defense ministry added that it hoped that the program would continue despite setbacks.[179]

Renegotiation talks continued into 2019. According to the agenda of a January 2019 meeting, Indonesia sought to extend its involvement in the program to 2031, and was interested in making part of its payments in trade for Indonesian-produced defense equipment.[43][180] By August, Indonesia had transport aircraft on offer along with commodities.[181][103]

In August 2021, Indonesia reaffirmed its commitment to the KF-21 program.[109] Cost negotiations were achieved and agreed by both parties in 2021.[110][111] In May 2022 it was reported that the issue of development payments had not yet been resolved.[112] In November 2022, it was reported that Indonesia had resumed payment for its share of the costs.[113]

On 13 June 2025, South Korea agreed to reduce Indonesia's contribution to 600 billion won ($439 million) through the signing of a memorandum of understanding at Indo Defence Expo & Forum 2024 in Jakarta.[182][183] DAPA had also met with Indonesian Minister of Defence Sjafrie Sjamsoeddin to reaffirm the joint partnership, while KAI and Indonesian Aerospace agreed to strengthen practical cooperation in production and marketing for the IF-21 variant.[184]

Indonesian engineers' alleged technology theft

On 2 February 2024, the South Korean National Intelligence Service (NIS) and the Defense Counterintelligence Command (DCC) announced a joint investigation into whether Indonesian engineers dispatched to KAI violated the Defense Technology Security Act for allegedly attempting to steal classified KF-21 technical data after storing it on an unauthorized USB drive.[185][186] According to the investigation authorities, on 17 January 2024, an Indonesian engineer was reported to have been caught attempting to take eight USB drives containing 49 confidential data related to KF-21 out of the company, and also included sensitive data of the European and U.S. subcontractors with restricted exports to third countries and avionics only accessible to KAI officials.[187][188]

On 11 March 2024, the Korean National Police Agency (KNPA), which is investigating the case at the request of DAPA, decided to expand its investigation after circumstantial evidence emerged that another Indonesian engineer was involved in the crime, and an initial investigation result report by NIS and DCC revealed that about 4,000 to 6,600 KF-21 data, including 3D design drawings of the aircraft, were stored on USB drives.[189]

On 15 March 2024, for an in-depth investigation, the security investigation department of the South Gyeongsang Provincial Police Agency dispatched 10 investigators to the Indonesian engineer's home and KAI office to conduct a search and seizure.[190]

South Korea is investigating Indonesian engineers for allegedly attempting to steal classified KF-21 "Boramae" fighter jet data. The suspects were caught storing information on unauthorized USB devices and are barred from leaving the country. Based on Korean CEO own statement there is no sensitive data on the USB and it is something that is shared with Indonesian team. (edit: the article doesn't confirm this.) Latest development shows that there is no proof on the technology stealing and it is stated by Korean government attorney. KAI CEO Kang Goo-young had hoped that the problem can be amicably resolved as he considered the partnership with Indonesia is still important in order to penetrate other markets such as for ASEAN and Islamic countries.[191][192]

In late May 2025, South Korean prosecutors concluded their investigation into five Indonesian engineers who had been under scrutiny for allegedly violating the Defense Technology Security Act, the Defense Acquisition Program Act, and the Foreign Trade Act. The prosecutors issued a non-indictment on those charges and granted suspended indictment (기소유예) for alleged violations of the Unfair Competition Prevention Act. A suspended indictment means that while the charges are acknowledged, the prosecutors chose not to proceed with prosecution in light of various mitigating circumstances. The investigation, which had lasted over a year and a half, was effectively concluded with this decision.[193]

Maeil Business Newspaper reported on 2 June 2025 that the five Indonesian engineers who were accused had been acquitted and suspended from prosecution.[194] The Indonesian Ministry of Foreign Affairs has reported that the 5 engineers are now home in good health and gathered with their families.[195]

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Variants

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KF-21 third prototype at 2022 Sacheon Airshow

Current variants

  • KF-21 Block I: The Block I focuses on the air-superiority capabilities,[196] though it is reported to include some air-to-ground functionality as well. Scheduled for deployment in 2026.
  • KF-21 Block II: With further development for the Block II, the KF-21 will evolve into a swing-role fighter, incorporating attack and reconnaissance capabilities.[197] It shares the same airframe as Block I, requiring only additional integration for expanded armament. Block I aircraft can be upgraded via software updates. Scheduled for deployment in 2028. Blocks I and II are designed to function as advanced 4.5+ generation fighters, offering greater survivability through reduced radar cross-section (RCS), more sophisticated avionics, and relatively cost-effective performance compared to alternative platforms in their class.[198]

Potential variants

  • KF-21 Block III (project name: KF-XX): Block III will be developed as a 5.5+ generation fighter jet, featuring internal weapons bays, enhanced stealth through radar-absorbent materials, and upgraded AESA radar with next-gen avionics. It will support unmanned teaming, network-centric warfare, and improved situational awareness. A domestically developed Korean engine is also planned to replace the current F414-GE-400, reducing foreign dependence.[199] Block III aims to combine high-end performance, survivability, and cost-effectiveness in a competitive fifth-generation platform.
    • KF-21EX: The KF-21EX is a planned advanced variant of the KF-21 Boramae that aims to significantly enhance the jet's strike capability, survivability, and operational effectiveness, particularly within a manned-unmanned teaming (MUM-T) construct. The most significant structural change in this upgraded version is the addition of an internal weapons bay, which allows the aircraft to carry munitions such as the GBU-31 Joint Direct Attack Munition (JDAM) and MBDA Meteor missiles without increasing its radar cross-section. This capability brings the KF-21EX to the strike power of fifth-generation fighters like the F-35. The aircraft will also receive several stealth-focused upgrades, including a reprofiled canopy, low-RCS radome, and new conformal antennas, to improve its survivability against radar threats. In its MUM-T role, the KF-21EX will serve as a manned command platform, working alongside future autonomous drones that will act as stand-in jammers to suppress enemy air defenses. To support this, the fighter will feature enhanced avionics, including an Electro-Optical Targeting System (EOTS), an upgraded electronic warfare suite, and potentially an AI-enabled mission computer and expendable decoys.[200]
    • KF-21EA: One of the three new variants revealed in June 2024. Will serve as an electronic warfare aircraft comparable to the EA-18G Growler. This variant would be based on the two-seat KF-21B, with a position at the back for the electronic warfare officer.[201]
    • KF-21SA: One of the three new variants revealed in June 2024. Will reportedly be a variant specifically dedicated to the export market, with opportunities for the client to modify the aircraft.[201]
  • KF-21N: In September 2022, KAI unveiled a model of the KF-21N, a carrier-based version of the fighter. In May 2022, the Ministry of National Defense (MND) decided to drop funding for the CVX, a planned small aircraft carrier capable of operating STOVL F-35B jets. It was later clarified that the MND would consider purchasing a larger aircraft carrier design, if a maritime jet fighter could be developed indigenously. Anticipating this, KAI began a preliminary design concept to make the KF-21 carrier-capable. The wings were 20% larger to ensure safety and stabilization when taking off and landing, and could fold for more compact storage. Structural changes would make the airframe capable of CATOBAR and STOBAR operations. KAI claimed it would be able to build the KF-21N "in a few years" if the Republic of Korea Navy (ROKN) decided to procure an aircraft carrier large enough to operate fighters,[202][203] but they instead decided to build a ship focused on controlling unmanned vehicles rather than carrying manned fighters.[204]
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Operators

Summarize
Perspective

Current operators

South Korea

Future operators

South Korea
  • Republic of Korea Air Force:
    • 18th Fighter Wing:
      • 20 KF-21 Block I ordered in June 2024 for a value of USD $1.41 billion.[155] The serial production started in July 2024.[156]
      • 20 additional KF-21 Block I ordered in June 2025.[158] The delivery of 40 units of KF-21 Block I will begin in September 2026 and be completed by 2028.[158]
      • 80 KF-21 Block II are planned to be ordered and delivered by 2032.[158]

Potential operators

Egypt
Egypt is regarded as a potential purchaser of the FA-50 as well as the newly-developed KF-21 Boramae fighter jet.[206]
India
Defence Blog Magazine reported that the KF-21 Boramae is being considered by the Indian Air Force (IAF) as a potential solution to its squadron shortages.[207] However, IAF officials have denied this, stating they have not been offered the platform, nor have they expressed interest in acquiring it.[208]
Indonesia
  • In 2016, Indonesia agrees to contribute approximately $1.25 billion (1.7 trillion won), representing 20% of the KF-21 development costs.[209]
  • 2017 was the last year Indonesia made a payment for several years.[209]
  • From January 2019 to November 2022, payments are halted by Indonesia.[210]
  • On November 2022, a payment is resumed.[210]
  • On February 2023, another payment is made. At this point, reports state Indonesia still owes more than 1.1 trillion won, having paid only 280 billion won.[210]
  • On June 2023, Indonesia fails to provide a payment schedule as promised.[210]
  • On October 2023, Indonesia fails again to provide a payment schedule.[211]
  • On August 2024, South Korea agrees to reduce Indonesia's financial contribution to 600 billion won (about $443 million) due to its persistent payment difficulties.[212]
  • On June 10, 2025, South Korea and Indonesia finalized an agreement that revised Indonesia's financial contribution to the KF-21 project. Out of the total project cost of 8.1 trillion won (approximately $5.9 billion), the updated contract reduces Indonesia’s share from 1.6 trillion won (approximately $1.168 billion, or 20% of the total) to 600 billion won (approximately $438 million, or 7.4%). The agreement reaffirms Indonesia’s planned purchase of 48 aircraft and the continued participation of PT DI in their production.[182]
Malaysia
Peru
Aiming for Peru's fighter jet contract, South Korea's Korea Aerospace Industries (KAI) signed a Memorandum of Understanding (MoU) with the Peruvian Air Force Maintenance Service (SEMAN) to manufacture KF-21 ‘Boramae’ fighter jet components in Peru.[215]
Philippines
In 2024, the Philippines announced its interest to purchase 40 jet fighters. The Gripen E/F and the F-16 Block 70/72 were pre-selected and South Korea joined the bid in September 2024 with the following jets:[216]
  • 10 KF-21 Block I with deliveries ahead of ROK Air Force
  • 12 FA-50 Block 20 (Block 70)
  • Upgrade of 12 FA-50PH to Block 20 (Block 70)
Poland
  • Polish defense company Polska Grupa Zbrojeniowa (PGZ) is reportedly keen to join South Korea's KF-21 fighter program, with a letter of intent expected to be issued soon, according to South Korean broadcaster MBC.[217]
  • In June 2025, a delegation from the Polish Air Force visited South Korea to inspect the production facilities of the FA-50 light combat aircraft. During the visit, the delegation also evaluated the KF-21 Boramae. Brigadier General Ireneusz Nowak, Inspector of the Polish Air Force, conducted a demonstration flight in the KF-21, as confirmed by Korea Aerospace Industries (KAI). The KF-21 is currently being offered to the Polish Air Force, which has expressed interest in acquiring an additional 32 multirole fighters to strengthen its combat capabilities.[218]
Saudi Arabia
  • On 30 January 2024, a South Korean Ministry of Defense official stated that senior representatives from the ministry and the Agency for Defense Development (ADD) made an unannounced visit to Saudi Arabia from 23 to 26 January. During the visit, the South Korean delegation met with Saudi Arabia's Deputy Defense Minister, Dr. Khalid bin Hussein Al-Biyari, and other officials to discuss the potential joint development of a 5th or 6th generation multi-role fighter based on the KAI KF-21 Boramae design.[219]
  • On 9 February 2025, an image from a presentation by KAI officials to Saudi Arabia regarding the KF-21 fighter jet briefly appeared on social media before being taken down.[220]
  • On July 29, 2025, Royal Saudi Air Force Commander Lieutenant General Turki bin Bandar bin Abdulaziz met with South Korean Air Force Chief of Staff General Lee Young-soo. The two discussed military cooperation and topics of mutual interest, including potential Saudi involvement in the KF-21 Boramae fighter jet project.[221]
  • On August 14, 2025, officials from Saudi military company SAMI Aerospace held a meeting with the Chief of Staff of the Republic of Korea Air Force to talk about boosting their partnership in the aviation sector.[222]
Spain
The KF-21 considered as options to fill the gap if FCAS program were to be canceled.[223]
United Arab Emirates
  • To strengthen its position in developing and exporting next-generation combat aircraft, South Korea has proposed joint development of the KF-21 and its successor to countries in Southeast Asia and the Middle East, with a particular focus on the United Arab Emirates and Saudi Arabia.[219]
  • On 15 May 2024, senior air force officials from South Korea and the United Arab Emirates (UAE) signed a letter of intent for comprehensive cooperation on South Korea's KF-21 Boramae. The agreement was signed by South Korean Air Force Chief of Staff General Lee Young-su and UAE Air Force and Air Defence Commander Major General Rashed Mohammed A.[224]
  • In April 2025, the United Arab Emirates Air Force and Air Defence, and the RoKAF signed a letter of intent to further the cooperation on the programme.[225]
  • On July 7th, 2025, a friendship flight took place at Sacheon Air Base in Gyeongnam, South Korea, involving high-ranking officials from both the Republic of Korea Air Force and the United Arab Emirates. ROKAF Chief of Staff General Lee Young-su piloted an FA-50 fighter jet, while UAE Assistant Undersecretary of the Ministry of Defense, Ibrahim Nasser Mohamed Al Alawi, flew in a prototype of the KF-21 Boramae fighter.[226]

Summary

More information Orders, Acquisition ...

Legend of the coloured numbers in the table:

  Systems assembled and produced in South Korea
  Systems assembled or produced outside of South Korea
  2nd hand sold/transferred [ – ] and bought/received [ + ]
  System upgraded, one variant to the other [ – ] / [ + ]
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Specifications (single seat aircraft)

Data from Korea Aerospace Industries,[227][228] Hanwha Systems[229] and LIG Nex1[230][231]

General characteristics

  • Crew: 1 or 2[4]
  • Length: 16.9 m (55 ft 4 in) [228]
  • Wingspan: 11.2 m (36 ft 7 in) [228]
  • Height: 4.7 m (15 ft 4 in) [228]
  • Wing area: 46.5 m2 (501 sq ft)
  • Empty weight: 11,800 kg (26,015 lb)
  • Gross weight: 17,200 kg (37,920 lb)
  • Max takeoff weight: 25,600 kg (56,400 lb) [227][228]
  • Fuel capacity: 6,000 kg (13,227 lb) internal[232]
  • Payload: 7,700 kg (17,000 lb) external[227][228]
  • Powerplant: 2 × General Electric F414-GE-400K (manufactured under license by Hanwha Aerospace) turbofan, 57.8 kN (13,000 lbf) thrust each [233] dry, 97.9 kN (22,000 lbf) with afterburner

Performance

  • Maximum speed: 2,200 km/h (1,400 mph, 1,200 kn) [227][228]
  • Maximum speed: Mach 1.81[234][32]
  • Combat range: 1,000 km (620 mi, 540 nmi) (estimated)[235]
  • Ferry range: 2,900 km (1,800 mi, 1,550 nmi) [227][228]

Armament

Avionics

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See also

Aircraft of comparable role, configuration, and era

References

Notes

External links

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