firm in Nizhny Novgorod and the Central Scientific Research Radio Engineering Institute in Moscow were selected for the development of the PAK FA's avionics suite. In April 2004, NPO Lyulka-Saturn (now NPO Saturn) was signed as the contractor for the AL-41F1 engines with the development designation izdeliye 117. Sukhoi used existing airframes as testbeds for various subsystems and concepts; the Su-47 tested internal weapon bays, and Su-27M prototypes served as testbeds for the flight control system and engines. To reduce developmental risk and spread out associated costs, as well as to bridge the gap with extant fourth generation fighters, Sukhoi implemented some of the T-50's technology and features, such as propulsion and certain avionics, in an advanced derivative of the Su-27 called the T-10BM (, ), which was eventually procured by the Russian Ministry of Defence in 2009 and entered service as the Su-35S in 2014. In December 2004, the T-50's conceptual design and shape was complete and approved by the Ministry of Defence; government funding of the programme began in 2005 and drastically increased in 2006 when detailed design was underway. On 8 August 2007, Russian Air Force Commander-in-Chief Alexander Zelin was quoted by Russian news agencies that the programme's development stage was complete and construction of the first aircraft for flight testing would begin, with three flyable T-50 prototypes planned to be built by 2009. In 2009, the aircraft's design was officially approved. The T-50 was named Su-57 in July 2017. Since the early stages of the PAK FA programme, Russia sought after foreign partnerships on the project to increase funding for its development and also secure large export orders. On 18 October 2007, Russia and India signed a contract for Sukhoi and Hindustan Aeronautics Limited (HAL) to jointly develop a derivative of the PAK FA called the Fifth Generation Fighter Aircraft (FGFA). In September 2010, India and Russia agreed on a preliminary design contract where each country was to invest $6 billion; a memorandum of understanding for the preliminary design was signed in December 2010, and the development of the FGFA was expected to take 8–10 years. By 2014, however, the Indian Air Force began voicing concerns over performance, cost, and workshare. India eventually left the partnership in 2018. Prototyping The T-50's maiden flight was repeatedly postponed from early 2007 after encountering unspecified technical problems. In August 2009, Alexander Zelin acknowledged that problems with the engine and