Question: The WS-15, code name Emei, is a Chinese after burning turbofan engine, a stealth, twinjet, fifth-generation fighter aircraft developed by China's Chengdu Aerospace Corporation for what airforce?
Sentence (from "Chengdu J-20"): The J-20 made its maiden flight on 11 January 2011, but the plane was officially revealed on China International Aviation & Aerospace Exhibition in 2016.
Relevant evidence: No