South Korea’s KF-21 Boramae fighter jet has flown in formation with American military aircraft for the first time, marking an important milestone for Seoul’s indigenous combat aviation programme and demonstrating growing operational interoperability between the South Korean and US air forces.
The historic formation flight took place over the Yellow Sea on October 23, 2026, involving the KF-21 alongside a US U-2S Dragon Lady high-altitude reconnaissance aircraft, F-35 Lightning II stealth fighters and F-16 Fighting Falcons. The flight was conducted ahead of the latest edition of Freedom Flag, the biannual joint air exercise between South Korea and the United States, which began on October 26.
The development is particularly significant because the KF-21 represents South Korea’s most ambitious effort to establish an independent military aircraft industry while maintaining close defence cooperation with Washington. It also comes more than a decade after the United States refused to transfer several sensitive technologies that Seoul initially sought for the fighter’s development.
Assigned to the 156th Fighter Squadron of the 16th Fighter Wing, the KF-21 participated in what officials described as a Friendship Flight. The Republic of Korea Air Force (RoKAF) also reportedly deployed F-35s, F-15Ks and FA-50 light combat aircraft as part of its broader formation.
Although the KF-21 was not formally included in the Freedom Flag exercise, its participation in the formation provided an opportunity to observe and gain experience alongside American aircraft before the commencement of the joint drills.
The US Seventh Air Force described the activity as an important demonstration of bilateral military integration.
“The Friendship Flight demonstrated the combined interoperability and combat readiness of the US Air Force [and Korean Air Forces] on the Korean Peninsula, showcasing how the air forces of both nations integrate directly during flying operations,” the command said.
The formation highlights how South Korea is positioning its new fighter within an established alliance-based military architecture while gradually reducing its dependence on foreign suppliers for critical combat aircraft technologies.
The KF-21 programme traces its origins to 2001, when then-President Kim Dae-jung proposed developing an indigenous South Korean fighter to strengthen the country’s aerospace and defence capabilities.
The programme subsequently evolved into a major national industrial undertaking, with the objective of producing a modern combat aircraft capable of replacing ageing fighters and reducing reliance on imported platforms.
However, one of the most challenging episodes came in 2015, when Washington declined to transfer four critical technologies that Seoul had sought through an offset arrangement associated with its purchase of F-35A Lightning II fighters.
The restricted technologies reportedly included an active electronically scanned array (AESA) radar, an infrared search-and-track (IRST) system, an electro-optical targeting pod and a radio-frequency jammer. These systems are essential to a modern fighter’s ability to detect and track targets, conduct precision engagements and defend itself against electronic threats.
The refusal was rooted in US export-control restrictions designed to protect sensitive military technologies. Nevertheless, it forced South Korea to pursue domestic alternatives rather than depend entirely on American technology.
South Korea subsequently developed much of the required technology through its domestic defence industry. Hanwha Systems took a leading role in developing the KF-21’s AESA radar, while South Korean companies also contributed to the aircraft’s IRST, electro-optical targeting and electronic warfare systems.
Seoul has said it secured approximately 87 per cent of the technologies required for the programme, while obtaining additional technological support from the United States.
The outcome has given the KF-21 an important industrial advantage. Because several critical mission systems are domestically developed, South Korea has greater control over their future modification, upgrades and potential export approvals.
According to GlobalData aerospace and defence analyst Udayini Aakunoor, the restrictions imposed by Washington have ultimately strengthened the aircraft’s commercial proposition.
“The US refusal to release the KF-21’s technologies have become the aircraft’s strongest selling point. With those systems now being Korean, Seoul can modify, upgrade and clear the KF-21’s mission systems for foreign buyers without seeking another government’s approval,” Aakunoor said in connection with GlobalData’s The Global Military Fixed Wing Aircraft Market 2026–2036 report.
However, the aircraft is not entirely independent of foreign technology. Its propulsion system consists of two General Electric F414 engines, highlighting the continuing importance of American industrial cooperation in the programme.
The KF-21 has placed South Korea among a relatively small group of countries capable of designing and producing advanced supersonic combat aircraft.
Manufactured by Korea Aerospace Industries (KAI), the aircraft is classified as a 4.5-generation fighter, placing it between conventional fourth-generation platforms and fifth-generation aircraft featuring comprehensive low-observable technology.
However, KAI has argued that the KF-21 offers capabilities approaching those of fifth-generation fighters.
KAI chief Kang Goo-young, a former Republic of Korea Air Force pilot, previously suggested that the conventional 4.5-generation classification understates the aircraft’s capabilities.
Comparing it with France’s Rafale and the European Eurofighter Typhoon, Kang described the KF-21 as a “4.9-generation fighter”, arguing that it is closer to fifth-generation aircraft than conventional 4.5-generation platforms.
The aircraft incorporates a stealth-conscious airframe design, an indigenous AESA radar, infrared search-and-track capabilities and electronic warfare equipment. However, unlike fully stealth-oriented fighters such as the F-35, its current configuration carries weapons on external hardpoints, limiting its ability to maintain a low radar signature during combat operations.
KAI and South Korea also plan to develop the fighter through a phased block-upgrade programme. The longer-term objective is to introduce Block III, also known as KF-21EX, with more advanced low-observable characteristics and capabilities associated with fifth-generation combat aircraft.
This approach would allow South Korea to improve the aircraft progressively rather than attempt to incorporate every advanced capability into the initial production configuration.
For the RoKAF, the programme is strategically important because it offers a domestically controlled platform that can operate alongside American F-35s and other allied aircraft while gradually strengthening South Korea’s independent air combat capabilities.
The KF-21 has also attracted attention because of the relatively rapid pace of its development and transition towards production.
The programme’s first prototype conducted its maiden flight in 2022, marking the beginning of an extensive flight-testing campaign. On March 25, 2026, KAI rolled out the first production KF-21 aircraft at its manufacturing facility in Sacheon, with President Lee Jae-myung attending the ceremony.
The transition from the first flight to the rollout of a production aircraft in less than five years represents a significant achievement for South Korea’s aerospace industry, particularly compared with the prolonged development cycles associated with several other advanced fighter programmes.
The first production aircraft was subsequently presented as South Korea prepared to introduce the fighter into its operational inventory.
In late September 2026, the KF-21 reached another milestone with its delivery to the Republic of Korea Air Force, accompanied by an official ceremony.
KAI has outlined an initial production plan involving 40 aircraft focused primarily on air-to-air combat capabilities, with deliveries expected by 2028. A further 80 aircraft equipped with long-range air-to-ground missiles are planned for delivery by 2032.
The programme is intended to replace the RoKAF’s ageing F-4 Phantom II and F-5 Tiger II fleets, while potentially reducing the service’s longer-term dependence on imported F-16 fighters.
The KF-21 is designed as a twin-engine, multirole supersonic combat aircraft. It has a reported maximum speed of Mach 1.81, an operational range of approximately 2,900 kilometres and a maximum payload capacity of 7,700 kilograms distributed across 10 external hardpoints.
The aircraft is being developed in both single-seat and two-seat configurations. The single-seat version is intended for operational missions, including air superiority and ground attack, while the two-seat variant provides additional flexibility for training and other operational requirements.
Its combination of modern sensors, electronic warfare capabilities, extended range and relatively advanced airframe is intended to provide the RoKAF with a substantial improvement over its older fighter fleet.
Beyond domestic military requirements, the KF-21 is central to South Korea’s ambition to become a major international defence supplier.
President Lee Jae-myung has previously emphasised the country’s intention to contribute to international peace and development by sharing not only advanced weapons systems but also technology and industrial development experience with partner countries.
The KF-21 could become an important component of that strategy, particularly among countries seeking modern combat aircraft without the acquisition costs, political conditions or technology-transfer restrictions sometimes associated with fifth-generation fighters.
South Korea’s domestic development of the radar, electronic warfare suite and other mission systems could provide additional flexibility when negotiating export agreements.
Nevertheless, the aircraft will face considerable competition. The American F-35 remains one of the world’s most advanced operational fighters, while the French Rafale, Eurofighter Typhoon and other established platforms already have significant international customer bases.
The KF-21’s ability to compete will therefore depend on its final operational performance, acquisition and maintenance costs, weapons integration, delivery schedules and the availability of export financing.
Its continuing reliance on US-made engines and other foreign components could also influence export negotiations, particularly where American export-control requirements apply.
The original South Korea-Indonesia partnership presents another dimension to the programme. Indonesia initially held a 20 per cent stake in the development project but subsequently saw its financial contribution and associated obligations reduced because of budgetary constraints. The arrangement has therefore evolved from the original level of bilateral participation.
Despite these challenges, the programme has continued to advance, reflecting Seoul’s determination to establish a sustainable domestic fighter manufacturing capability.
The first formation flight with American aircraft on October 23 demonstrates that this ambition does not require South Korea to distance itself from its principal security partner.
Instead, Seoul appears to be pursuing a dual-track strategy: developing greater technological independence while ensuring that its military equipment remains compatible with the United States and other allied forces.
The KF-21 still has years of operational testing, weapons integration and capability upgrades ahead before reaching its full potential. Its first joint formation with American aircraft, however, marks an important step in that journey.
For South Korea, the objective is no longer simply to manufacture a fighter jet at home. It is to build an advanced combat aircraft that can strengthen national defence, support an expanding global arms industry and operate seamlessly alongside the military platforms of its closest allies.
