Korea's indigenous KF-21 fighter jet has made its first formation flight with U.S. aircraft over the West Sea, Seoul officials said Friday. The KF-21 Boramae, assigned to the 156th Fighter Squadron, 16th Fighter Wing, conducted the joint aerial formation flight with U.S. Air Force jets last Friday, according to military officials. The U.S. side deployed the U-2S Dragon Lady, a high-altitude reconnaissance aircraft, and the F-35 and F-16 fighter jets, whereas the Korean Air Force mobilized its F-35, F-15K and FA-50 fighter jets, along with the KF-21 Boramae. It marked the first time the KF-21 Boramae has flown in formation with U.S. air force assets. The formation flight came shortly before the allies launched their biannual combined air drills, dubbed Freedom Flag, on Monday, aimed at enhancing the joint interoperability of their forces. A Korean Air Force official explained that the flight was aimed at accumulating experience for the KF-21 ahead of the Freedom Flag drills. "The Friendship Flight demonstrated the combined interoperability and combat readiness of the U.S. Air Force and ROKA