The U.S. military conducted a rare joint training exercise featuring both variants of its advanced F-35 stealth fighter at a South Korean air base last Friday, a day before North Korea tested upgraded surface-to-air missiles it described as designed to counter “various aerial targets such as unmanned attack drones and cruise missiles.”

The training at Kunsan Air Base – which NK News was invited to observe on an exclusive basis among English language media – marked an uncommon exercise featuring both Air Force F-35A Lightning IIs and Marine Corps F-35B variants operating together on the Korean Peninsula, according to U.S. Forces Korea officials.