![Undated file photo shows China\'s J-20 stealth fighter jet takes off for a night confrontation training mission during a coordinated tactical training exercise with J-16 fighter jets and J-10c fighter jets in an effort to boost the PLA Air Force\'s combat capability. (Photo/eng.chinamil.com.cn)](http://www.ecns.cn/hd/2018/06/02/983b07a35bcb485aa6c206bb4602f059.jpg)
Undated file photo shows China's J-20 stealth fighter jet takes off for a night confrontation training mission during a coordinated tactical training exercise with J-16 fighter jets and J-10c fighter jets in an effort to boost the PLA Air Force's combat capability. (Photo/eng.chinamil.com.cn)
![Undated file photo shows China\'s J-20 stealth fighter jet takes off for a night confrontation training mission during a coordinated tactical training exercise with J-16 fighter jets and J-10c fighter jets in an effort to boost the PLA Air Force\'s combat capability. (Photo/eng.chinamil.com.cn)](http://www.ecns.cn/hd/2018/06/02/5cf0821309ec441c93ca4e1b9a60496e.jpg)
Undated file photo shows China's J-20 stealth fighter jet takes off for a night confrontation training mission during a coordinated tactical training exercise with J-16 fighter jets and J-10c fighter jets in an effort to boost the PLA Air Force's combat capability. (Photo/eng.chinamil.com.cn)