A prototype of South Korea's first locally developed KF-21 fighter jet, which successfully completed its first test flight last week, also passed a second round of trials.

According to Korea Aerospace Industries(KAI) on Friday, the prototype operated for 39 minutes after taking off from the runway of the Third Flying Training Wing in Sacheon, South Gyeongsang Province, at 11:02 a.m.

The KF-21 flew at a speed of around 400 kilometers per hour, similar to the previous flight, but retracted its landing gear, reportedly demonstrating the stability of the jet engine.

South Korea undertook the eight-point-eight trillion-won project starting in 2015 with the objective of replacing the Air Force's fleet of older F-4 and F-5 jets by 2032.

Indonesia had signed a partnership to shoulder 20 percent of the Phase One development program.

Upon completion of the jet development, South Korea will become the world's eighth country capable of manufacturing locally developed supersonic fighter jets.