influences, woven into the structure. This allows a more efficient maintenance and repair process. The Su-57 could also serve as a testbed for advanced AI and man-unmanned teaming technologies intended for use in a future sixth-generation fighter program. The aircraft has also tested autonomous flight without pilot input. Operational history Testing and trials Even before the first flight of the T-50 prototype, several subsystems were tested on other aircraft for validation and risk reduction; an Su-27M was used to test the AL-41F1 engine on 21 January 2010, while another tested the KSU-50 flight control system. The T-50 prototype conducted its first high speed taxi run on 21 January 2010 and had its maiden flight several days later on 29 January 2010. First supersonic flight occurred on 14 March 2011 at a test range near Komsomolsk-on-Amur. The Su-57 tests consisted of preliminary trials PI (, ) conducted by Sukhoi at the Gromov Flight Research Institute (LII) () at Zhukovsky, as well as two stages of joint state trials GSI (, ) conducted by the Ministry of Defence at the 929th State Flight Test Centre named for V. P. Chkalov at Akhtubinsk. The completion of GSI-1 resulted in the acceptance of the aircraft's airworthiness, and the completion of GSI-2, which tests the mission systems and armaments, clears the Su-57 for operational service. The preliminary trials and state trials occurred with some overlap with each other. Early flight tests revealed that the initial T-50 design had problems with structural strength and fatigue; when the first two prototypes were showcased publicly in MAKS-2011, the airframes cracked despite flying with a restrictive 5–g limit, which necessitated grounding and structural reinforcing for over a year as well as a “second stage” structural redesign. Of the ten flying and three non-flying T-50 prototypes, the three non-flying prototypes tested static flight loads, one each for "first stage" and "second stage" structures, and avionics integration. The first two flying prototypes tested flight characteristics and basic mechanical systems, and thus had no mission systems. Testing of mission systems such as the radar and electronic warfare suite began from the third prototype onwards, with each subsequent aircraft having slight variations in the arrangement of avionics and sensor systems. The final pre-production aircraft were equipped with full mission systems and tested the overall integrated avionics. By February 2014, the first phase of preliminary trials, PI-1, had concluded; in the same month, the