South Korea’s Defense Acquisition Program Administration claims the KF-21 is a 4.5-generation fighter jet because it lacks an internal weapons bay that increases stealthiness.
On Apr. 9, 2021 South Korea unveiled its homegrown KF-21 Boramae (Hawk) supersonic stealth jet fighter.
According to the Republic of Korea Armed Forces Facebook page, the first flight of KF-21 (former KF-X) will take place about a year from now. Total of 8 prototypes (6 flying & 2 ground testing) will undergo rigorous testings until mass production begins in 2026, with a goal of 40 jets deployed by 2028 and 120 by 2032.
Once operational, the KF-21 will be armed with both air-to-air and air-to-surface missiles — and possibly even air-launched cruise missiles.
The Boramae is a twin-engine fighter and will come in single- and two-seat versions.

“A new era of independent defense has begun, and it’s a historic milestone in the development of the [South Korean] aviation industry,” President Moon Jae-in said at the rollout of the KF-21, at the production plant of Korea Aerospace Industries (KAI) in Sacheon, South Gyeongsang province.
As reported by CNN, while South Korea’s Defense Acquisition Program Administration (DAPA) claims the KF-21 is a 4.5-generation fighter jet because it lacks, for instance, an internal weapons bay that increases stealthiness, analysts say it may be able to fly higher and faster than the newest US-made fifth-generation fighter, the F-35, and still carry a robust weapons load.
According to KAI, the aircraft is designed to be able to fly at a maximum speed of Mach 1.81, with its flying range reaching 2,900 kilometers.
Featuring dimension of 16.9m x 4.7m x 11.2m, KF-X is larger than F-16 and is of similar size as F-18. Development of KF-21 began in earnest on January 2016 and the assembly process began in 2019 after Critical Design Review (CDR) was completed in 2018. The KF-21 is expected to replace Republic of Korea Air Force (ROKAF) F-4 and F-5 (and eventually even F-15K and KF-16) fighters and will operate alongside the more advanced F-35A in ROKAF inventory.

The KF-21 is a joint project between South Korea and Indonesia in which Seoul holds 80% of shares while Jakarta seeks 20%. South Korea says Indonesia is behind in payments to the project, but negotiations continue and Jakarta’s defense minister was at Friday’s rollout.
Moon saluted Indonesia for its role. “In particular, I thank the Indonesian government for becoming a partner who believed in the potential of South Korea,” he said.
While the KF-21 might replace hundreds of fighter jets in ROKAF‘s fleet, given that its price tag is expected to be significantly lower than the F-35s the US sells to foreign militaries it also has significant export potential.
In fact since countries such as Thailand, the Philippines, and Iraq all operate the same kind of aircraft the KF-21 will replace in ROKAF fleet could be leading clients for the fighter.

Photo credit: KAI/Republic of Korea Armed Forces