Notable changes have been observed in both of China’s sixth-generation fighter programmes, with updated prototypes seen flying just 10 months after their first public appearance, indicating rapid progress as the country vies with the US for air supremacy. Photos circulating on Chinese social media since Tuesday showed what appeared to be Chengdu Aircraft Corporation’s sixth-generation fighter, bearing a tailless and three-engine design, conducting a test flight. Unofficially referred to as the…