China Built the World's Best-Looking Stealth Fighter — But Couldn't Build Its Engine

Modern fighter aircraft development requires not just advanced airframe design but also mastery of jet engine technology, which involves decades of accumulated expertise in manufacturing single-crystal turbine blades with microscopic cooling channels; this knowledge cannot be copied through espionage or reverse engineering, as demonstrated by China's 15-year struggle to develop the WS-15 engine for the J-20 stealth fighter, which ultimately succeeded after years of failures and significant investment.