In a major demonstration of military muscle, US and South Korean airforces held their largest ever joint aerial drills on Monday amid rising tensions with Pyongyang.
Around 230 aircraft, including some of the Pentagon's most powerful planes, were expected to take part in the exercises.
The drills, called Vigilant Ace, came less than a week after North Korea said it had tested its most advanced ballistic missile.
In a statement South Korea's defence ministry spokesman Moon Sang-Gyun said: "South Korea's Air Force Operations Command and the US Seventh Air Force will conduct Vigilant Ace drills from today until December 8 to improve the airforces wartime operations capabilities."
Over the weekend both US and North Korean officials warned that the likelihood of war in the region is increasing, with Kim Jong Un's regime insisting the US and South Korean military manoeuvres would push the Korean peninsula to "the brink of nuclear war".
Russia and China have also urged the US and South Korea to call off the drills amid fears exercises could provoke a backlash from Pyongyang.
