SEOUL, April 17 (Yonhap) -- South Korea and the United States kicked off large-scale combined air drills on Monday, the South's Air Force said, amid joint efforts to sharpen deterrence against Pyongyang's military threats.

About 110 aircraft and more than 1,400 troops were mobilized for this year's Korea Flying Training (KFT), which got under way earlier in the day for a 12-day run at Gwangju Air Base in Gwangju, 267 kilometers south of Seoul, according to the armed service.

More than 60 South Korean warplanes, including F-35A, F-15K and KF-16 fighters, will join the drills, while the U.S. will deploy some 40 aircraft, such as its Air Force's F-16 fighters, A-10 attack aircraft and the Marine Corps' F-35B and FA-18 jets.

The exercise will focus on enhancing the interoperability and combined operational capability of the allies' advanced fighters by conducting various drills, such as a strike package flight and close air support operations, according to the South's Air Force.

KFT is one of the two regular large-scale exercises the allies hold every year. KFT is held in the first half of the year, while the other -- named Vigilant Storm last year -- in the latter half.

The exercise comes as tensions run high on the Korean Peninsula, following Pyongyang's test-firing of what it claimed to be a solid-fuel intercontinental ballistic missile Thursday and a North Korean patrol boat's crossing of the western de facto maritime border Saturday.