South Korea’s Very Own KF-21 5th-Gen Stealth Fighter Takes to Sky

By Kris Osborn, President, Center for Military Modernization

South Korea is surging ahead with its first indigenously constructed stealth fighter jet called the KAI KF-21 Borame, a 5th-generation aircraft likely to support and network with the countries’ F-35 force. The effort is a collaborative venture between South Korea and Indonesia which picks up 20-percent of the developmental costs.

This KAI KF-21 Borame, a fighter jet formerly called KAI KF-X, first took to the sky in 2022. The aircraft is reported to be stealth but reportedly lacks a 5th-generation-like internal weapons bay. The prototype Borame’s speed is listed on spec sheets at Mach 1.8, something considerably slower than an F-22 but slightly faster than the 1.6 Mach speeds listed for the F-35.

A write up in Aero Corner says the KF-21 “measures 55 feet 5 inches, will be able to reach Mach 1.81 via 2×Hanwha Techwin General Electric F414-KI afterburning turbofans, and will carry Taurus KEPD 350 air-to-ground missiles and MBDA Meteor, IRIS-T, AIM-120 AMRAAM, and AIM-9 Sidewinder air-to-air missiles.”

Much like Japan’s Mitsubish F-X to an extent, the KF-21 looks like a blend between the F-22 and F-35. It has two engines like an F-22, yet its main fuselage and vertical tail wings look very similar to the F-35. Other attributes of the KF-21 include expected modern radar systems such as an Active Electronically Scanned Array (AESA), mission computer and high-tech multi-function digital display. AESA radar is quite significant as it can track multiple threats at one time and deliver a targeting return “rendering” for pilot crews to attack enemy targets.

KF-21 Stop China? Network with F-35?

The existence of this aircraft, which could clearly contribute in a significant way to collective efforts to deter China, introduces a number of key questions and a host of unclear variables. Initially, one might wonder about South Korea’s industrial infrastructure and commensurate ability to manufacture a sizeable fleet of new 5th-gen aircraft. Secondly, should there be a robust fleet, it seems if would be critical to ensure it can successfully network with the F-35, as Japan, South Korea, Singapore and Australia all operate F-35s along with forward-operating US Navy and Marine Corps F-35s as well. If the KF-21 could operate as an extension of a combat envelope or air formation campaign, such an aircraft could provide a tremendous advantage. Perhaps the South Korean-Indonesian aircraft can be engineered with some kind of datalink able to integrated with the F-35s Multifunction Advanced Data Link (MADL).