in technical research remained unsolved. On 28 February 2009, Sukhoi general director Mikhail Pogosyan announced that the airframe was almost finished and that the first prototype should be ready by August 2009. On 20 August 2009, Pogosyan said that the first flight would be by year's end. Konstantin Makiyenko, deputy head of the Moscow-based Centre for Analysis of Strategies and Technologies said that "even with delays", the aircraft would likely make its first flight by January or February, adding that it would take five to ten years for commercial production. Flight testing was further delayed when Deputy Prime Minister Sergei Ivanov announced in December 2009 that the first trials would begin in 2010. The first taxi test was successfully completed on 24 December 2009, and the maiden flight of the first prototype aircraft, T-50-1, occurred on 29 January 2010. Piloted by Sukhoi test pilot Sergey Bogdan, the aircraft's 47-minute maiden flight took place at KnAAPO's Dzemgi Airport in the Russian Far East. Construction of the prototypes would progress slower than initially planned; by the end of October 2013, the test programme had amassed more than 450 flights across five aircraft. A total of ten flying and three non-flying T-50 prototypes would be built for preliminary flight tests and state trials. Initially, the program was planned to have up to six prototypes before the start of serial production; however testing would reveal that the initial prototypes did not have adequate fatigue life, with early structural cracks forming in the airframe. The aircraft subsequently underwent a structural redesign, with changes including increased composite material usage, reinforced airframe to meet full life cycle requirements, elongated tail "sting", and slightly greater wingspan; the sixth flyable prototype was the first of the redesigned "second stage" aircraft, with the five initial prototypes consequently considered "first stage" vehicles and requiring additional structural reinforcements in order to continue flight tests. The last two flying prototypes were test articles of production Su-57 aircraft with full mission systems on board. While the "second stage" structural redesign reduced the weight growth from the required strengthening of the "first stage" design, the normal takeoff weight still increased to approximately . Issues and accidents during the testing resulted in repeated delays to the programme, with the delivery of the first production aircraft pushed back from 2015 to 2020. Procurement The procurement plans for the PAK FA have been considerably scaled back and delayed