The Yak-9U is the last version which was at war. It is one of «green» Yak-9U fitted with small oil cooler wingroot intakes, narrow section, water cooler and as wing tips, as Yak-9M had. Furthermore, there isn't bullet-proof windscreen. The aircraft was adopt to serial production in a hurry. So despite high flight performance of experimental specimens the fighter considered as unreliable in combat regiments.