South Korea and the U.S. scrambled more than 130 warplanes as the “Vigilant Defense” air drills got under way over the Korean Peninsula.

According to the South Korean Air Force, the drills, which began on Monday and will run through Friday, will provide intensive training for actual situations with simulations of 24-hour wartime operations.

The South Korean Air Force is sortieing fifth-generation F-35s, of which it currently operates 40 with plans to purchase 25 more in a five billion-dollar deal approved by the U.S. State Department in September.

The U.S. is sending F-35, F-16, and A-10 fighters along with other attack aircraft from both bases in Japan and the mainland to conduct joint drills with South Korean forces that include live fire air-to-surface drills among other emergency exercises.

Previous aerial training in the South have often been met with provocations by the North, such as a test firing of multiple short-range ballistic missiles in response to last year's "Vigilant Storm" exercises.