South Korea and the United States began Friday massive eight-day air defense drills aimed at bolstering their operational capabilities, Air Force here said.

Some 50 fighter jets, including F-15Ks from South Korea and F- 16 from the U.S., and 250 pilots are taking part in the exercises, dubbed “Max Thunder,” in the western part of the South Korean airspace.

Led by the South Korean air force, the exercises include a hypothetical air battle and defeating a possible provocation by the Democratic People’s Republic of Korea (DPRK).

The two allies have engaged in several joint military maneuvers since the fatal March sinking of a South Korean warship, blamed on the DPRK. The DPRK denies its responsibility.