S. Korea's indigenous KF-21 fighter jet conducts 1st formation flight with US aircraft

South Korea’s KF-21 Boramae completed its first formation flight with U.S. Air Force aircraft. The flight took place over the Yellow Sea before the allies began their Freedom Flag air drills. It was an important step because the KF-21 had not previously flown in formation with U.S. air force assets.

The United States sent a U-2S Dragon Lady reconnaissance aircraft, plus F-35 and F-16 fighter jets. South Korea sent its own F-35, F-15K, and FA-50 fighters, along with the KF-21. The aircraft flew together as part of what the U.S. Seventh Air Force called the Friendship Flight.

A Korean Air Force official said the flight helped build experience for the KF-21 before Freedom Flag began. It also demonstrated how the two air forces can operate together during flying operations. That experience is intended to support combined readiness and interoperability on the Korean Peninsula.

The KF-21 Boramae is South Korea’s first fighter jet built with indigenous technology. It is a domestically developed aircraft intended to become a central asset for the South Korean Air Force. Its development matters because it represents a major national effort to create a modern fighter while replacing older aircraft in the fleet.

In this context, indigenous technology means the fighter’s development was completed using South Korean technological and industrial capabilities. The article does not specify which individual systems were designed domestically. It does state that South Korea completed development in July, officially ending a project launched in 2015.

The KF-21 is now moving from development into service. Its first production model was assigned to the 16th Fighter Wing last month. South Korea plans to deploy more aircraft by mid to late 2027 and make the KF-21 a central air force asset by deploying more than 100 by early 2030.

The formation included aircraft with different roles and capabilities from both air forces. The United States deployed the U-2S Dragon Lady, a high-altitude reconnaissance aircraft, along with F-35 and F-16 fighter jets. South Korea contributed F-35, F-15K, and FA-50 fighter jets, as well as the KF-21 Boramae.

The most important aircraft for South Korea was the KF-21 because this was its first formation flight with U.S. air force assets. The mixture allowed the two forces to practice operating together across a broader group of aircraft. It also gave the newly assigned fighter experience before the Freedom Flag drills.

The planned fleet is large. The Air Force intends to deploy more than 100 KF-21 fighter jets by early 2030 and operate them as a central asset. More aircraft are scheduled for deployment by mid to late 2027, following the assignment of the first production model to the 16th Fighter Wing.

South Korea and the United States conducted the flight before Freedom Flag to prepare their forces for the combined air drills. The KF-21 was newly entering service, so the Korean Air Force wanted to build experience before the larger exercise began. The flight therefore served as an early opportunity to practice operating with American aircraft.

The timing was deliberate. The formation occurred shortly before the allies launched their biannual Freedom Flag drills on Monday. It included U.S. F-35 and F-16 fighters, a U-2S reconnaissance aircraft, and South Korean F-35, F-15K, FA-50, and KF-21 jets. The U.S. Seventh Air Force called the event the Friendship Flight.

The broader goal was stronger cooperation in the air. Officials said the flight demonstrated combined interoperability and combat readiness. Practicing together beforehand could help the two forces coordinate more smoothly during Freedom Flag and future flying operations on the Korean Peninsula.

Interoperability is the ability of two forces to work together effectively during operations. For air forces, that includes coordinating aircraft movements, communicating, sharing relevant information, and following compatible procedures. The article describes it as the direct integration of U.S. and South Korean forces during flying operations.

The Friendship Flight provided a practical example. A U.S. U-2S flew with American F-35 and F-16 fighters, while South Korean F-35, F-15K, FA-50, and KF-21 aircraft joined the formation. This gave the KF-21 experience operating alongside U.S. air force assets before Freedom Flag.

The likely improvement is combined combat readiness. The U.S. Seventh Air Force said the flight demonstrated interoperability and readiness on the Korean Peninsula. Repeated practice can help both forces coordinate more smoothly and understand how their aircraft integrate during shared flying operations. The article does not identify specific future mission outcomes.

South Korea began the KF-21 project to replace its Air Force’s aging fleet of U.S.-made F-4 and F-5 fighter jets. The need to replace those aircraft is the main reason the project was launched in 2015. The KF-21 therefore connects fleet modernization with South Korea’s effort to build a fighter using indigenous technology.

The replacement process has now reached production and deployment. South Korea completed development of the KF-21 in July. The first production model was assigned to the 16th Fighter Wing last month. That assignment marked a move from a long development project toward regular operational use.

The Air Force plans to deploy more KF-21s by mid to late 2027. It expects to deploy over 100 by early 2030 and operate them as a central asset. The article does not give the exact retirement schedule for the F-4 and F-5 fleets, but it identifies the KF-21 as their planned replacement.

In modern air operations, fighter jets and reconnaissance aircraft support different parts of the same effort. Fighters are designed for combat and air protection. Reconnaissance aircraft collect information from the air. Combined exercises allow crews and aircraft to practice coordinating those functions under shared procedures. These general roles are established military knowledge; the article gives only a brief description.

The flight illustrated the basic pattern. The United States sent the U-2S Dragon Lady, identified as a high-altitude reconnaissance aircraft, with F-35 and F-16 fighters. South Korea sent F-35, F-15K, FA-50, and KF-21 fighters. They flew together in formation over the Yellow Sea.

The exercise mattered because it built experience and interoperability. The KF-21 practiced flying with U.S. assets before Freedom Flag. The U.S. Seventh Air Force said the flight showed how both air forces could integrate directly and demonstrate combined combat readiness.