On December 27, 2015, China's official news agency Xinhua published slightly blurry photos that show a plane parked on a runway at an unidentified military airfield, coated in a yellowish paint typically used before the application of radar absorption material. The jet was identical to ones believed to be J-20 prototypes seen in public in previous years. But the key difference was the number painted below the cockpit – “2101”. Earlier versions were numbered 2012 or 2017 or some variation of the final two digits. Xinhua reported that the appearance of 2101 “may indicate the J-20 has moved from the test flight period to initial mass production”, adding the arrival of the final stage would not be surprising.