SEOUL-- A homegrown KF-21 fighter prototype achieved supersonic speeds in a test flight Tuesday, South Korea's state arms procurement agency said, in a key milestone for the high-profile warplane development project.

The first KF-21 prototype reached the speed of Mach 1, or 1,224 kilometers per hour, at an altitude of 40,000 feet at 3:15 p.m. as it flew over the country's southern waters, according to the Defense Acquisition Program Administration (DAPA).

The prototype flew for 56 minutes after taking off from the Air Force's 3rd Flying Training Wing in Sacheon, about 300 km south of Seoul. It made its maiden flight in July last year.

Defense Minister Lee Jong-sup hailed the development as a "historic" feat.

"Through the success in the supersonic-speed flight, our military further solidified the foundation to construct a robust military based on science and technology," Lee was quoted by DAPA as saying. "We also took one step further to the goal of becoming the world's fourth largest defense exporter."

Securing the supersonic capability is a major part of the development efforts, led by its manufacturer, Korea Aerospace Industries Ltd., as it means key functions work smoothly irrespective of flight speeds.

DAPA said it confirmed the "structural stability" of the KF-21 aircraft during the supersonic flight, while emphasizing the feat as being based on domestically developed technologies.

Three KF-21 prototypes have so far conducted more than 80 flight tests to expand its capabilities in terms of altitude, speed and other elements, since the first prototype began the testing process in July.

DAPA has said it plans to use a total of six prototypes, including the three, to conduct some 2,000 flight tests in total by February 2026.

Launched in 2015, the KF-21 project worth 8.8 trillion won (US$7.09 billion) seeks to develop the 4.5th-generation fighter to replace the country's aging fleet of F-4 and F-5 jets waiting to be decommissioned following decades of service.

Source: Yonhap News Agency