South Korea has successfully completed all planned development flight tests of the KF-21 Boramae, its domestically developed 4.5-generation multirole fighter jet, marking a major milestone in the country’s indigenous defense aviation program. 

According to the Defense Acquisition Program Administration (DAPA), the final test flight was conducted on January 12, 2026, over the southern sea off Sacheon, in South Gyeongsang Province, using the fourth prototype aircraft.

The completion of the final sortie brings to a close approximately 42 months of development flight testing, formally ending the aircraft’s full development flight test phase.

The KF-21 flight test program involved six prototype aircraft, which together accumulated around 1,600 accident-free sorties. 

This figure was reduced from an initially planned 2,000 flights due to the use of extended-duration missions and efficient test planning, including aerial refueling operations.

Across these sorties, engineers verified more than 13,000 individual test conditions, covering a wide range of critical performance and systems checks.

These included flight stability, high-angle-of-attack maneuvers, supersonic flight, aerial refueling capability, and advanced avionics integration.

Key subsystems tested included the indigenously developed AESA radar, as well as air-to-air weapons separation and live firing trials, confirming the aircraft’s core combat capabilities.

The KF-21 Boramae — formerly known as the KF-X program — is South Korea’s first domestically developed supersonic fighter aircraft. The project is led by Korea Aerospace Industries (KAI) in cooperation with the Agency for Defense Development and more than 225 domestic companies, reflecting a broad national industrial effort.

The aircraft is intended to replace the Republic of Korea Air Force’s aging F-4 Phantom II and F-5 fighter fleets, while significantly enhancing the country’s technological self-reliance.

The first prototype rollout took place in April 2021, followed by the maiden flight on July 19, 2022.

The KF-21 is powered by twin GE F414 engines and features advanced avionics, a reduced radar signature design, and semi-stealth characteristics.

The aircraft is designed to integrate modern Western weapons systems, including Meteor and IRIS-T air-to-air missiles, positioning it as a capable multirole platform for regional air superiority missions.

With flight testing complete, system development is expected to conclude in the first half of 2026.

Deliveries of mass-produced aircraft to the Republic of Korea Air Force (ROKAF) are scheduled to begin in the second half of 2026.

Initial Block I aircraft will focus primarily on air-to-air combat roles.

More advanced Block II variants, incorporating full air-to-ground and anti-ship capabilities, are planned for introduction from early 2027.

South Korea aims to field up to 120 KF-21 fighters by the early 2030s.

The successful, incident-free completion of the KF-21’s development flight tests ahead of schedule highlights the program’s maturity and South Korea’s growing aerospace and defense capabilities.

It places the country among a small group of nations capable of independently designing and producing advanced combat aircraft, while also attracting export interest from countries including the UAE, Poland, and others.