South Korea officially kicked off its multibillion-dollar project Thursday to produce homemade fighter jets over the next decade.

Under the Korean Fighter Experimental project by the Defense Acquisition Program Administration, contractor airplane maker Korea Aerospace Industries Ltd. will come up with six units of a homegrown prototype fighter by 2021.

The test fighters will undergo flight tests for four years before the development project is completed by mid-2026, according to DAPA.

Based on the complete design, KAI will manufacture 120 fighter jets from 2026 through 2032 to replace the Air Force's aging fleet of F-4 and F-5 fighters, DAPA said.

DAPA held a meeting with KAI and military officials from Indonesia earlier in the day in the KAI's factory in Sacheon, South Gyeongsang Province, to officially start the project.

Indonesia is the KAI's foreign partner for the fighter jet project, having signed a contract last year to finance 20 percent of the cost in the development phase.

Under the deal, Indonesia will also be entitled to acquire the aviation technology of the project and bring home one experimental airplane.

"The KF-X project will take the role to lead the development of our aviation industry," DAPA Minister Chang Myoung-jin said during the meeting. "DAPA will develop a locally made fighter jet, which all South Koreans can be proud of."  

Worth some 18 trillion won, the project is aimed at developing a twin-engine, 4.5 generation multirole fighter equipped with an active electronically scanned array radar, which is much more advanced than the passive electronically scanned array radar that's currently in service.

The formal inauguration of the project comes after months of intense controversy, which flared up after the U.S. government refused last year to issue an export license on four combat jet technologies American defense giant Lockheed Martin sought to provide to South Korea.

Through an offset deal linked to South Korea's purchase of 40 units of Lockheed Martin's F-35 Lightning II fighters in 2014, South Korea had sought 25 kinds of fighter technologies from the U.S. firm, but Washington refused to permit the transfer of four of them, including the AESA radar technology.

In the fallout, DAPA commissioned the state-run Agency for Defense Development to develop the radar.

Including the AESA radar, around 65 percent of the KF-X fighter's components will be made domestically, according to DAPA.

For the transfer of the rest of the 21 technologies, Seoul is currently under negotiations with Washington, which are expected to take up to three years. (Yonhap)