South Korea has unveiled the first mass-produced KF-21 Boramae fighter jet, developed jointly with Indonesia. The focus now shifts to global marketability, potentially increasing South Korea’s standing as an arms exporter.

South Korea has spent a decade and billions of dollars trying to build a world-class fighter jet. Now that the finish line is drawing near, it’s nearly time to find out who will buy one. The first mass-produced KF-21 Boramae, developed jointly with Indonesia since 2015, was unveiled by Korea Aerospace Industries in Sacheon on March 25. Analysts say the aircraft could pave the way for South Korea, already one of the world’s top 10 arms exporters, to grab an even bigger slice of the global...