Complex sentence: In late December 2015, a new J-20 numbered 2101 was spotted; it is believed to be the low rate initial production (LRIP) version of the aircraft.
Split into simpler sentences: In late December, 2015, a brand new J-20 numbered 2101 was spotted. The 2101 was believed to be the low rate initial production (LRIP) version of the aircraft.