A J-10 fighter jet attached to an aviation brigade of the air force under the PLA Southern Theater Command takes off for a sortie during a round-the-clock flight training exercise on March 26, 2019. Such "two-on-two" and "two-on-one" free air-to-air combats were carried out during the training to improve the all-weather combat capability of pilots. (eng.chinamil.com.cn/Photo by Wei Jinxin)