South Korean F-35A stealth fighter jets fly in formation during Armed Forces Day celebrations in Gyeryong, South Korea, on September 29. (Photo: Reuters)

The annual drills, called Vigilant Defense, will run until Friday, featuring variants of the F-35 stealth fighter from both the United States and South Korea, among other aircraft, South Korea’s Air Force said. 

The drills are aimed at improving interoperability between the two militaries by performing major air missions such as air-to-surface live fire drills, defensive counter air operation and other emergency training. 

North Korea has long condemned joint drills between the United States and South Korea as a rehearsal for invasion and proof of hostile policies by Washington and Seoul.