Undated photo shows Chinese Air Force jet fighters attending the "Red Arrow -- 2018" drill. The Chinese Air Force began the "Red Arrow -- 2018" combat exercise in the country's northwest desert on May 23, 2018. (Xinhua/Xi Bobo)

BEIJING, May 23 (Xinhua) -- The Chinese People's Liberation Army (PLA) air force on Wednesday began its regular annual combat exercise in the country's northwest desert.

The "Red Arrow -- 2018" drill involved nearly 100 aircraft including fighter jets, bombers, early warning and reconnaissance aircraft, radars and surface-to-air missiles, according to the PLA air force.

The purpose of the exercise is to train the capabilities of the air force's command centers, it said.

The "Red Arrow" series has been a signature for the PLA air force's realistic combat exercises for the past 18 years.