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KAI KF-21 Boramae
“Fighting Hawk”

Q: Can I fly in a KF-21?

No. The KAI KF-21 Boramae is a front-line military fighter still in testing and early production, with no public passenger-flight programme. You can, however, fly in several genuine military jets today via MiGFlug.

Q: Is the KF-21 a stealth fighter?

Only partly. It is a 4.5-generation jet with stealth-influenced shaping, but the initial Block I and II aircraft carry weapons externally, which increases radar cross-section. A future variant with an internal weapons bay and lower signature is planned but does not yet exist, so it is semi-stealthy rather than a full fifth-generation stealth fighter.

Q: Who builds the KF-21 Boramae?

Korea Aerospace Industries (KAI) of South Korea is the prime contractor, with the ROK government funding most of the programme and Indonesia as a risk-sharing partner. Major systems such as the AESA radar were developed domestically by companies including Hanwha Systems.

Q: What engines does the KF-21 use?

Two General Electric F414-GE-400K afterburning turbofans, each about 97.9 kN (22,000 lbf) with afterburner, assembled in Korea by Hanwha Aerospace. It is the same engine family used by the F/A-18E/F Super Hornet.

South Korea’s first indigenous fighter — a twin-engine 4.5-generation multirole jet, still maturing through testing and early production, built to retire the ageing F-4 and F-5.

~Mach 1.8Reported top speed

2022First flight · 19 July

6Flight-test prototypes

40Block I jets ordered by the ROKAF

Photo: KF-21A / Wikimedia Commons · CC BY-SA 4.0

RoleMultirole fighter (4.5-generation)EraModern · 21st centuryEngine2 × GE F414-GE-400KOriginSouth Korea · KAIStatusIn testing / early productionWant to fly a fighter jet yourself?

The Story

South Korea builds its own fighter

For decades South Korea flew American fighters — F-4 Phantoms, F-5 Tigers, F-16s and later F-15Ks. The ambition to build a home-grown fighter dates to a presidential pledge in 2001, but it took until 2015 for Korea Aerospace Industries (KAI) to win the full-scale development contract for what was then called KF-X. The goal was a twin-engine, 4.5-generati)on multirole fighter to replace the Republic of Korea Air Force’s retiring F-4D/E Phantom II and F-5E/F Tiger II fleets, with a home-built radar and a level of stealth shaping short of a true fifth-generation jet.

The programme is a genuinely new aircraft, and much about it is still being proven. The first prototype was rolled out in April 2021 and made its maiden flight on 19 July 2022. Six prototypes — four single-seat and two twin-seat — flew a development test programme that Korean officials say wrapped up in January 2026 after around 1,600 sorties. The ROKAF has ordered an initial batch of 40 Block I aircraft, with deliveries reported to begin around 2026. These are early days: the KF-21 is best described as in development and entering low-rate production, not as a mature front-line type.

From the start the KF-21 has been an international as well as a national project. Indonesia joined in 2016 as a risk-sharing partner under the parallel IF-X designation, originally committing to roughly a fifth of the development cost in exchange for technology and local assembly. That contribution has been repeatedly contested and, in June 2025, renegotiated sharply downward — a reminder that the aircraft’s programme, like its flight envelope, is still being worked out.

A brand-new fighter, still being proven — ambitious, largely indigenous, and not yet fully mature.The KF-21 story — Korea’s first home-built fighter

01The KAI KF-21 Boramae’s origins: how South Korea set out to build its own fighter

The idea of a Korean-designed fighter was announced by President Kim Dae-jung in 2001, but the KF-X project spent years in feasibility studies and cost debate before KAI signed the full-scale development contract in 2015. South Korea funds the large majority of the programme; Indonesia signed on in 2016 as a risk-sharing partner, and US firms and Lockheed Martin provided some technology transfer, though several sensitive technologies (including key stealth and AESA elements) were withheld and had to be developed at home.

The result is often described as a stepping stone between the FA-50 light fighter KAI already built and a possible future fifth-generation aircraft. It is important to hedge the claims made for it: many performance and cost figures come from the manufacturer or the Korean government and have not been independently verified in combat or long-term service, because the type is only now entering production.

Design & Engineering

What makes it special

A largely home-built fighter with an indigenous AESA radar

The KF-21’s headline achievement is that South Korea developed much of it domestically, including an indigenous active electronically scanned array (AESA) radar led by Hanwha Systems with LIG Nex1 — a capability only a handful of countries possess. Several sensitive technologies were denied by the United States during development, so Korea built its own. As with any new radar, its real-world performance is still being validated in flight test.

Two proven GE F414 engines

Rather than gamble on a new powerplant, the KF-21 uses two General Electric F414-GE-400K afterburning turbofans — the same family that powers the F/A-18E/F Super Hornet — each rated at roughly 97.9 kN (about 22,000 lbf) in reheat, assembled in Korea by Hanwha Aerospace. The twin-engine layout gives the reported ~Mach 1.8 top speed and redundancy the single-engine FA-50 lacks.

Semi-stealth now, internal weapons planned later

The KF-21 is a 4.5-generation design: it uses radar-cross-section-reducing shaping and internal-bay provisions, but the early Block I and Block II jets carry weapons externally on ten hardpoints. A future variant (often referred to as KF-21EX) is planned to add an internal weapons bay and greater stealth — so its fifth-generation credentials remain a goal, not a delivered fact.

02The KF-21 Boramae’s radar and sensors: why the home-built AESA matters

When the KF-X programme began, the United States declined to transfer four key technologies — among them the AESA radar, infrared search-and-track and electronic-warfare suites. Rather than abandon the project, South Korea funded domestic development, with Hanwha Systems and the Agency for Defense Development producing a national AESA radar that was fitted to the prototypes and tested in flight from the mid-2020s. Independent verification of its detection range and reliability is limited, and figures cited for it should be read as manufacturer or ministry claims until the type has served operationally.

03The KF-21’s stealth: a 4.5-generation jet, not an F-35 rival

The KF-21 is deliberately positioned as a 4.5-generation fighter. It borrows stealth-influenced shaping — canted tails, a faceted forward fuselage and internal routing — but the initial production aircraft carry missiles and bombs externally, which sharply increases radar cross-section compared with a true fifth-generation type such as the F-35. KAI has spoken of a later variant with an internal weapons bay and reduced signature, sometimes labelled KF-21EX, but that aircraft does not yet exist. Any description of the KF-21 as a “stealth fighter” should be qualified: it is semi-stealthy by design intent, with full low-observability reserved for a future step.

Technical Data

Full specifications

Figures are for the single-seat KF-21 as published by the manufacturer and Korean government. Because the aircraft is still in testing and early production, many values are provisional and should be treated as reported rather than combat-proven.

Airframe & Performance

Crew: 1 (twin-seat variant seats 2)
Length: ~16.9 m
Wingspan: ~11.2 m
Height: ~4.7 m
Empty weight: ~11,800 kg
Max takeoff weight: ~25,600 kg
Max speed: ~Mach 1.8 (~2,200 km/h, reported)
Service ceiling: ~16,800 m (~55,000 ft)
Combat radius: ~1,000 km (estimated)
Load factor: reported +9 / −3 g class

Propulsion, Armament & Cost

Engines: 2 × GE F414-GE-400K
Thrust (each): ~97.9 kN (~22,000 lbf) with afterburner
Radar: Indigenous AESA (Hanwha Systems)
Cannon: 1 × internal M61A2 20 mm Vulcan
Hardpoints: 10 · ~7,700 kg external load
First flight: 19 July 2022
Unit cost: ~US$80–110 million (estimate)
Cost per flight hour: No official public figure yet

04The KF-21 Boramae’s cost: what a new indigenous fighter is estimated to cost

Development of the KF-21 has been budgeted at roughly 8.6 trillion won (on the order of US$6–7 billion) for research and development, with total programme spending including procurement reported near 18 trillion won over its life. Per-aircraft flyaway cost has been estimated at around US$80–110 million, though published figures have drifted upward and vary with exchange rates and block standard — treat any single number as an estimate.

No reliable cost-per-flight-hour figure exists in open sources yet, which is unsurprising for an aircraft that has only just finished its development flight-test programme. Operating-cost claims for the type are, for now, projections rather than measured data.

Timeline

From national ambition to first jets

2001

The ambition is announced

President Kim Dae-jung pledges that South Korea will develop its own fighter — the seed of the KF-X programme.

2015

Development contract

KAI wins the full-scale development contract for the KF-X, beginning detailed design of the aircraft.

2016

Indonesia joins

Indonesia signs on as a risk-sharing partner under the IF-X name, initially committing to about a fifth of the cost.

2021

Roll-out

The first prototype is unveiled in April 2021 and formally named Boramae; ground and taxi testing follow.

2022

First flight

The KF-21 makes its maiden flight on 19 July 2022, opening a multi-year flight-test campaign.

2024

First production contract

South Korea places an initial mass-production order, beginning the shift from prototypes to service aircraft.

2025

Indonesia’s share is cut

Seoul and Jakarta agree to reduce Indonesia’s contribution by roughly two thirds amid unpaid instalments.

2026

Testing done, deliveries begin

Korean officials report the development flight-test programme complete after ~1,600 sorties; early deliveries to the ROKAF begin.

Stories & Eyewitnesses

Twelve KF-21 stories

Origins

A fighter Korea vowed to build

The KF-21 grew from a 2001 presidential pledge that South Korea would design its own jet.

Read the full story

South Korea had licence-built and imported Western fighters for decades when, in 2001, President Kim Dae-jung publicly committed the country to developing an indigenous fighter. The idea — then called KF-X — spent years in feasibility studies and budget fights before KAI won the development contract in 2015. The KF-21 is the aircraft that ambition finally produced, though whether it fully meets its original goals will only become clear as it enters service.

Partnership

Indonesia signs on

In 2016 Indonesia joined as a risk-sharing partner under the IF-X designation.

Read the full story

From 2016 the programme was binational: Indonesia agreed to fund roughly a fifth of development in return for technology transfer and local assembly of jets it would call IF-X. The arrangement gave the project scale and a launch export customer, but Jakarta’s payments repeatedly fell behind, and the partnership has been renegotiated more than once — a running uncertainty rather than a settled fact.

Roll-out

Unveiled before it flew

The first KF-21 was rolled out and named Boramae in April 2021, over a year before its first flight.

Read the full story

KAI unveiled the first prototype at a ceremony in April 2021, with the aircraft formally christened Boramae — a young hawk. The roll-out was a national milestone broadcast widely in Korea, but it is worth remembering that a roll-out is a presentation, not a flying aircraft: the prototype still faced more than a year of ground and taxi tests before it left the runway.

First flight

19 July 2022

The KF-21 made its maiden flight in July 2022, becoming a genuinely flying prototype.

Read the full story

On 19 July 2022 a KF-21 prototype lifted off for a roughly half-hour first flight, landing gear down, escorted by chase aircraft. It marked the transition from mock-up and taxi trials to a real flight-test programme — and made South Korea one of a small group of nations to fly a domestically developed supersonic fighter.

Testing

Six prototypes, 1,600 sorties

A fleet of six prototypes flew the development test programme, reported complete in early 2026.

Read the full story

Six prototypes — four single-seat and two twin-seat airframes — carried out the flight-test campaign, expanding the envelope, firing weapons and testing the radar. Korean officials reported the development phase complete in January 2026 after around 1,600 sorties. Such figures come from the programme itself; independent confirmation of maturity will come only with operational service.

Radar

A homegrown AESA

After the US withheld radar technology, Korea built its own AESA for the jet.

Read the full story

One of the KF-21’s defining features is its indigenous active electronically scanned array radar, developed by Hanwha Systems and partners after the United States declined to transfer the technology. Building a national fighter radar is something only a few countries manage. Its real-world performance, however, is still being validated — the published detection ranges are manufacturer figures, not service-proven numbers.

Propulsion

Two American engines

The KF-21 flies on a pair of proven General Electric F414 turbofans.

Read the full story

For power the KF-21 relies on two General Electric F414-GE-400K afterburning turbofans, the same engine family used by the F/A-18E/F Super Hornet, assembled in Korea by Hanwha Aerospace. Choosing a mature, imported engine reduced the risk in an already ambitious programme — a pragmatic decision that keeps the “indigenous” label focused on the airframe, avionics and radar rather than the powerplant.

Stealth

4.5-gen, not 5th

The KF-21 is semi-stealthy by design, but carries its weapons externally for now.

Read the full story

The KF-21 uses shaping to reduce its radar signature, but the early Block I and Block II aircraft hang missiles and bombs on external hardpoints, which undoes much of that stealth. KAI describes it as a 4.5-generation fighter and has spoken of a later variant with an internal weapons bay and lower observability. Until that jet exists, calling the KF-21 a “stealth fighter” overstates what is flying today.

Name

What Boramae means

The jet’s name comes from a Korean word for a young hunting hawk.

Read the full story

Boramae is a Korean term for a young hawk trained for falconry — a fitting emblem for a first-generation home-built fighter. The name was chosen through a public naming effort and announced at the 2021 roll-out. It is sometimes rendered in English as “Fighting Hawk” or “Young Hawk.”

Production

The first orders

South Korea has ordered an initial 40 Block I jets, with more expected.

Read the full story

The ROKAF plans to buy on the order of 120 KF-21s over time, beginning with an initial batch of about 40 Block I aircraft optimised for air-to-air work. Early production contracts were placed from around 2024, with deliveries reported to begin in the mid-2020s. Block II, adding stronger air-to-ground capability, is planned to follow — but these are early production numbers for an aircraft still finding its feet.

Partnership

A contested bill

In 2025 Indonesia’s share of the cost was cut by roughly two thirds.

Read the full story

Indonesia had committed to around 1.7 trillion won — about a fifth of development cost — but fell behind on payments. In June 2025 Seoul agreed to reduce Jakarta’s obligation to about 600 billion won, and the scope of technology transfer and even the promised prototype were left subject to further negotiation. Reports through 2026 suggested Indonesia might step back from co-production entirely, underlining how unsettled the partnership remains.

Future

The road ahead

Korea hopes to grow the KF-21 into a stealthier jet and win export orders.

Read the full story

KAI’s roadmap points toward a more capable KF-21 with an internal weapons bay and reduced signature, alongside export marketing to countries such as the Philippines and the UAE. Whether those ambitions are realised depends on funding, further development and a competitive export market. For now the KF-21 is a promising, largely home-grown fighter at the very start of its career — not a finished product.

Gallery

The KF-21 in pictures

A KF-21 Boramae prototype on the flightline South Koreas first home-built fighter. — A KF-21 Boramae prototype on the flightline — South Korea’s first home-built fighter.Photo: KF-21A / Wikimedia Commons · CC BY-SA 4.0

A side view of the KF-21 Boramae, showing its twin-tail, F-16-generation-plus planform.Photo: dooyeol Choi / Wikimedia Commons · CC BY 3.0

The sixth KF-21 prototype on the ramp six airframes flew the development test programme. — The sixth KF-21 prototype on the ramp — six airframes flew the development test programme.Photo: Peppsi Wings / Wikimedia Commons · CC BY 3.0

A KF-21 prototype on public display at the 2022 Sacheon Airshow in South Korea.Photo: dooyeol Choi / Wikimedia Commons · CC BY 3.0

A head-on view of the KF-21, showing its twin-engine, stealth-influenced shaping.Photo: AnShmat / Wikimedia Commons · CC BY-SA 4.0

A KF-21 with external stores early jets carry weapons externally on ten hardpoints. — A KF-21 with external stores — early jets carry weapons externally on ten hardpoints.Photo: AnShmat / Wikimedia Commons · CC BY 4.0

Watch

The KF-21 in motion

A curated video feature for the KF-21 Boramae is coming soon. In the meantime, explore the photo gallery above and the operator map below.

Operations

Where the KF-21 operates

Service Status

Where the record stands

The KF-21 has no combat record — it is a new aircraft only now entering service, and everything about its capability is, for the moment, based on testing and manufacturer data rather than operational use. Its story so far is measured in prototypes flown, test points cleared and the first production orders placed, not in missions flown. That is exactly what to expect from a fighter in development and early production.

~1,600Development test sorties (reported)

6Prototypes built and flown

40Block I jets on initial order

Compare the combat record of every military aircraft. Figures as of July 2026.

Questions & Answers

Everything people ask about the KF-21

Can I fly in a KF-21?

No — the KAI KF-21 Boramae is a front-line military fighter still in testing and early production, and there is no public passenger-flight programme for it. You can, however, fly in several genuine military jets today — see migflug.com/flights-prices/.

Is the KF-21 a stealth fighter?

Only partly. It is a 4.5-generation jet with stealth-influenced shaping, but the initial Block I and Block II aircraft carry weapons externally, which greatly increases radar cross-section. A future variant with an internal weapons bay and lower signature is planned but does not yet exist, so it is best described as semi-stealthy rather than a full fifth-generation stealth fighter.

Who builds the KF-21 Boramae?

Korea Aerospace Industries (KAI) of South Korea is the prime contractor, with the Republic of Korea government funding most of the programme and Indonesia as a risk-sharing partner. Major systems such as the AESA radar were developed domestically by companies including Hanwha Systems.

What engines does the KF-21 use?

Two General Electric F414-GE-400K afterburning turbofans, each about 97.9 kN (22,000 lbf) with afterburner, assembled in Korea by Hanwha Aerospace. It is the same engine family used by the F/A-18E/F Super Hornet.

Is the KF-21 in service yet?

It is only just entering service. The type first flew in July 2022, and Korean officials reported the development flight-test programme complete in early 2026, with deliveries of an initial batch of about 40 Block I aircraft to the ROKAF beginning around the mid-2020s. It is best described as in early production rather than fully operational.

What is Indonesia’s role in the KF-21?

Indonesia joined in 2016 as a risk-sharing partner under the IF-X name, originally committing to roughly a fifth of development cost in exchange for technology and local assembly. Its payments fell behind, and in June 2025 its contribution was renegotiated down by about two thirds; its long-term participation has remained uncertain.

What will the KF-21 replace?

It is intended to replace the Republic of Korea Air Force’s ageing F-4 Phantom II and F-5 Tiger II fighters, filling the gap between the light FA-50 and heavier types such as the F-15K and F-35A.

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