South Korean official said in September that the KF-X fighter program it's working on with Indonesia passed key design reviews.

This month, South Korea put the first full-size mock-up of the KF-X on display at the Seoul International air show.

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SEONGNAM, South Korea (Reuters) — South Korea has displayed the first full-size mock-up of the KF-X fighter jet it is developing with Indonesia, after officials said the program passed key design reviews in September.

The next-generation aircraft being developed by Korea Aerospace Industries (KAI) is designed to be a cheaper, less-stealthy alternative to the US-built F-35, and the plan is to eventually replace most of South Korea's older fighter jets and produce more for export.

The mock-up was displayed on Monday at the Seoul International Aerospace and Defense Exhibition (ADEX).

South Korea has ordered 40 of the advanced F-35A aircraft from the United States, the first of which arrived this year. North Korea has condemned South Korea's purchase of the F-35s, as well as the development of other advanced weapons.

KAI is currently manufacturing a KF-X prototype and plans to carry out ground testing and flight tests in 2021 and 2022, respectively, company officials said.