Question: The Advanced Tactical Fighter (ATF) was a demonstration and validation program undertaken by the United States Air Force, including the Soviet Sukhoi Su-27, a twin-engine supermaneuverable fighter aircraft designed by Sukhoi, it was designed to complement which aircraft?
Sentence (from "Sukhoi Su-27"): The Sukhoi Su-27 (Russian: Сухой Су-27 ; NATO reporting name: Flanker; nicknamed "Sushka" in USSR) is a twin-engine supermaneuverable fighter aircraft designed by Sukhoi.
Relevant evidence: No