constructed. Working in cooperation with Sukhoi, KnAAPO's own engineers designed the Su-35UB so as to combine thrust-vectoring engines with features of the Su-27M. Modified from an Su-30MKK airframe, the aircraft made its first flight on 7 August 2000, and afterwards served as an avionics test-bed. While the original Su-27M never entered mass production due to a lack of funding, Sukhoi refined the Su-27M's use of canards and the Su-37's thrust-vectoring technology and later applied them to the Su-30MKI two-seat fighter for the Indian Air Force. The tenth Su-27M (T10M-10) also served as a test-bed for the Saturn AL-41FS engine that is intended for the Sukhoi Su-57 (previously known under the acronym "PAK FA") jet fighter. Modernization With the need to update Russia's aging fleet of Su-27 aircraft, Sukhoi and KnAAPO in 2002 started integrating glass cockpits and improved weapons-control systems (to accommodate a greater variety of weapons) to existing air force aircraft. The Su-27SM, as the modified aircraft is called, made its first flight in December 2002. The initial success of this project led Sukhoi in December 2003 to proceed with a follow-up modernization programme. Known internally as T-10BM, the programme was aimed at a more thorough redesign of the airframe to narrow the qualitative gap between Russian aircraft and foreign fourth-generation aircraft. The resultant design, also designated Su-35, would serve as an interim solution pending the introduction of the Sukhoi Su-57 fifth-generation fighter, many features of which the aircraft would incorporate. Additionally, the aircraft was to be a single-seat alternative to the two-seat design of the Su-30MK on the export market. In many respects, the T-10BM design outwardly resembles the Su-27 more than the Su-27M. During tests of the thrust-vectoring engines and the Su-27M's aerodynamic layout, Sukhoi had concluded that the loss of manoeuvrability due to the removal of the canards – the design of which imposed a weight penalty on the airframe – could be compensated for by the addition of thrust-vectoring nozzles. Industry progress in the fields of avionics and radars have also reduced the weight and size of such components, which shifted the centre of gravity of an aircraft rearward. Therefore, designers removed the canards (and the dorsal air brake) found on the Su-27M; the size of the vertical tails, aft-cockpit hump and tail boom were also reduced. With such changes, as well as the increased use of aluminium and titanium alloys and composites, designers had