Yes, each aero-engine has its own unique infrared characteristics, which can be clearly distinguished. (mentioned in the top secret flight of American movies), the infrared detection distance is not small (the American space early warning satellite is the infrared detection ballistic missile tail flame, which is far enough), and it is easy to be disturbed. The main defects of stealth aircraft are high cost, precise instruments but low reliability, strict shape requirements, and the maximum load is the price. But these shortcomings are acceptable compared with their advantages, so countries are scrambling to develop stealth aircraft.