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?

full_context: Document 1: Sukhoi Su-47: The Sukhoi Su-47 "Berkut" (Russian: Сухой Су-47 Беркут—"Golden Eagle" ) (NATO reporting name Firkin), also designated S-32 and S-37 (not to be confused with the twin-engined delta canard design offered by Sukhoi in the early 1990s under the designation Su-37) during initial development, was an experimental supersonic jet fighter developed by Sukhoi Aviation Corporation. A distinguishing feature of the aircraft was its forward-swept wing that gave the aircraft excellent agility and maneuverability. While serial production of the type never materialized, the sole aircraft produced served as a technology demonstrator prototype for a number of advanced technologies later used in the 4.5 generation fighter SU-35BM and current fifth-generation jet fighter prototype Sukhoi Su-57.
Document 2: General Electric YF120: The General Electric YF120 was a variable cycle turbofan engine designed by GE Aircraft Engines in the late 1980s/early 1990s for the United States Air Force's Advanced Tactical Fighter (ATF) project (which resulted in the F-22 Raptor). GE lost the engine competition for this aircraft to Pratt & Whitney F119.
Document 3: Sixth-generation jet fighter: A sixth-generation jet fighter is a conceptualized class of fighter aircraft design more advanced than the fifth-generation jet fighters that are currently in service in the United States and in development in other countries. The United States Air Force (USAF) and United States Navy (USN) are anticipated to field their first sixth-generation fighters in the 2025–30 time frame. The USAF is pursuing development and acquisition of a sixth-generation fighter through the F-X program to complement existing platforms in service such as the Lockheed Martin F-22 Raptor. The USN is pursuing a similar program called the Next Generation Air Dominance, likewise intended to complement and/or replace its existing aircraft such as the Boeing F/A-18E/F Super Hornet.
Document 4: Advanced Tactical Fighter: The Advanced Tactical Fighter (ATF) was a demonstration and validation program undertaken by the United States Air Force to develop a next-generation air superiority fighter to counter emerging worldwide threats, including Soviet Sukhoi Su-27 and Mikoyan MiG-29 fighters under development in the 1980s. Lockheed and Northrop were selected in 1986 to develop the YF-22 and the YF-23 technology demonstrator aircraft. These aircraft were evaluated in 1991 and the Lockheed YF-22 was selected and later developed into the F-22 Raptor.
Document 5: Sukhoi Su-57: The Sukhoi Su-57 (Russian: Сухой Су-57 ) is the designation intended for a stealth, single-seat, twin-engine jet multirole fighter aircraft designed for air superiority and attack operations. The aircraft is the product of the PAK FA (Russian: ПАК ФА , Russian: Перспективный авиационный комплекс фронтовой авиации , "Perspektivny Aviatsionny Kompleks Frontovoy Aviatsii", literally "Prospective Airborne Complex of Frontline Aviation"), a fifth-generation fighter programme of the Russian Air Force. Sukhoi's internal name for the aircraft is T-50. The Su-57 will be the first aircraft in Russian military service to use stealth technology. The fighter is planned to have supercruise, stealth, supermaneuverability and advanced avionics to overcome the prior generation fighter aircraft as well as ground and maritime defences.
Document 6: 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. It was intended as a direct competitor for the large United States fourth-generation fighters such as the Grumman F-14 Tomcat and F-15 Eagle, with 3530 km range, heavy aircraft ordnance, sophisticated avionics and high maneuverability. The Su-27 was designed for air superiority missions, and subsequent variants are able to perform almost all aerial warfare operations. It was designed with the Mikoyan MiG-29 as its complement.
Document 7: Sukhoi Su-30MKK: The Sukhoi Su-30MKK (NATO reporting name: Flanker-G) is a modification of the Sukhoi Su-30, incorporating advanced technology from the Sukhoi Su-35 variant. The Su-30MKK was developed by Sukhoi in 1997, as a result of a direct Request for tender between the Russian Federation and China. It is a heavy class, all-weather, long-range strike fighter, and like the Sukhoi Su-30, comparable to the American McDonnell Douglas F-15E Strike Eagle. Su-30MK2 is a further improvement to Su-30MKK with upgraded avionics and maritime strike capabilities. The MKK and MK2 are currently operated by the People's Liberation Army Air Force, Indonesian Air Force, Vietnam People's Air Force, Venezuelan Air Force and the Ugandan Air Force.
Document 8: Mikoyan MiG-29: The Mikoyan MiG-29 (Russian: Микоян МиГ-29 ; NATO reporting name: Fulcrum) is a twin-engine jet fighter aircraft designed in the Soviet Union. Developed by the Mikoyan design bureau as an air superiority fighter during the 1970s, the MiG-29, along with the larger Sukhoi Su-27, was developed to counter new American fighters such as the McDonnell Douglas F-15 Eagle, and the General Dynamics F-16 Fighting Falcon. The MiG-29 entered service with the Soviet Air Force in 1982.
Document 9: Sukhoi Su-37: The Sukhoi Su-37 (NATO reporting name: Flanker-F) is an experimental single-seat, supermaneuverable multirole jet fighter, designed by Sukhoi. A further development of the original Su-27 "Flanker", it was modified from the first-generation Su-35 (formerly "T10M") prototypes. The Su-37 features an upgraded avionic suite and fire-control system but its most notable additions are the thrust vectoring nozzles; only one prototype was converted.
Document 10: Lockheed YF-22: The Lockheed/Boeing/General Dynamics YF-22 was an American single-seat, twin-engine fighter aircraft technology demonstrator designed for the United States Air Force (USAF). The design was a finalist in the USAF's Advanced Tactical Fighter competition, and two prototypes were built for the demonstration/validation phase of the competition. The YF-22 won the contest against the Northrop YF-23, and entered production as the Lockheed Martin F-22 Raptor. The YF-22 has similar aerodynamic layout and configuration as the F-22, but with differences in the position and design of the cockpit, tail fins and wings, and in internal structural layout.
Document 11: Lockheed Martin F-22 Raptor: The Lockheed Martin F-22 Raptor is a fifth-generation, single-seat, twin-engine, all-weather stealth tactical fighter aircraft developed for the United States Air Force (USAF). The result of the USAF's Advanced Tactical Fighter program, the aircraft was designed primarily as an air superiority fighter, but also has ground attack, electronic warfare, and signal intelligence capabilities. The prime contractor, Lockheed Martin, built most of the F-22's airframe and weapons systems and conducted final assembly, while Boeing provided the wings, aft fuselage, avionics integration, and training systems.
Document 12: Northrop YF-23: The Northrop/McDonnell Douglas YF-23 was an American single-seat, twin-engine stealth fighter aircraft technology demonstrator designed for the United States Air Force (USAF). The design was a finalist in the USAF's Advanced Tactical Fighter (ATF) competition, battling the Lockheed YF-22 for a production contract. Two YF-23 prototypes were built, nicknamed "Black Widow II" and "Gray Ghost".
Document 13: Sukhoi Su-30: The Sukhoi Su-30 (Russian: Сухой Су-30 ; NATO reporting name: Flanker-C) is a twin-engine, two-seat supermaneuverable fighter aircraft developed by Russia's Sukhoi Aviation Corporation. It is a multirole fighter for all-weather, air-to-air and air-to-surface deep interdiction missions.
Document 14: M-ATF: The M-ATF program was originally a project between Russia and Iran to produce a fourth+ generation fighter plane that would be excellent for developing nations who want to become self-sufficient and self-reliant. The program was eventually abandoned by Russia and Iran, though now some evidence has become available that Iran has either revived the program or using it to advance its Shafaq program. The program traces its roots to the Russian cancelled Mikoyan Project LFI program; the aircraft was also referred to as the MiG-I-2000 or Vityaz2000.A model of the original aircraft was shown at Iran Airshow 2005.
Document 15: Sukhoi Su-25: The Sukhoi Su-25 "Grach" (Russian: Грач ("rook"); NATO reporting name: Frogfoot) is a single-seat, twin-engine jet aircraft developed in the Soviet Union by Sukhoi. It was designed to provide close air support for the Soviet Ground Forces. The first prototype made its maiden flight on 22 February 1975. After testing, the aircraft went into series production in 1978 at Tbilisi in the Georgian Soviet Socialist Republic.
ground_truth: Mikoyan MiG-29