Sukhoi began modernizing the Su-35 in the mid-2000s to provide a 4.5-type generation fighter making use of current technologies.The modernized Su-35 will be interim design until the fifth generation PAK FA (T-50) enters service.The modernized Su-35 has been referred to as "Su-35BM" ( Big Modernization) by some sources, but Sukhoi simply refers to the fighter as "Su-35". The modernized Su-35 is considered to be 4++ generation by Sukhoi.

The new design has a reinforced airframe for longer service life and has a reduced radar signature from the front. The modernized Su-35's new nose holds an improved passive electronically scanned array radar and the aircraft featured many other upgrades to its avionics and electronic systems, including digital fly-by-wire and a rear-looking radar for firing Semi-Active Radar missiles. In the 1990s, a two-dimensional asymmetric thrust vectoring system was first tested on the Su-35 and served as a basis for further development of the Su-37. For the Su-35BM, a new type of 2D thrust vectoring engine, the 117S, has been developed and replaces the current AL-31F or AL-35.

Contrary to the designs of the original Su-35 and Sukhoi's other recent machines - the Su-30MKIand the Su-37 - the new Su-35 omits the canard and speed brake. The canards were needed to increase/maintain maneuverability due to the addition of more modern, and heavier hardware in the nose area, compared to the original Su-27. A disadvantage of the canards is they significantly increase radar returns and drag, thus decreasing efficiency, speed, range, and weapons-carrying capacity. The Su-35 uses composite materials and newer electronics to make the aircraft lighter, especially in the nose area. This allowed Sukhoi's designers to do away with the canards and their disadvantages while still keeping up high operational system characteristics. The lighter new design has actually allowed an increase in both fuel and weapons-carrying capacity as compared to earlier Su-27 fighters. To maintain maneuverability equal to or greater than canard-equipped fighters, the Su-35 uses fully-rotating vectoring thrust nozzles on its new powerful Saturn engines.The cockpit has been redesigned with two LCD screens and compatibility with helmet-mounted displays. The Su-35BM's software has added compatibility with new weapons systems. Other new avionics include a long-range information targeting and jam-resistant datalink capability and an electronic reconnaissance system. Newer, lighter systems have been added (including a brand new FBO (Fly by Optics) flight-control system and OLS). The avionics are integrated with the GLONASS radio-based satellite navigation system.

The Su-37 is derived from the original Su-35, which was initially designated Su-27M. A Su-27M prototype (T-10S-70) first flew in 1988. Changes from the Su-27 include canards, upgraded engines, new radar, and a digital fly by wire flight control system. Sukhoi changed the Su-27M's designation to Su-35 in 1993. Later Su-35 prototypes added a glass cockpit and modified tailfins. The Su-35 design was modified into the Su-37 by adding 2D thrust vectoring nozzles.The first Su-37 test aircraft made its maiden flight in April 1996 equipped with vectoring nozzles. The Su-37 appeared at the 1996 Farnborough airshow piloted by Sukhoi test pilot Yevgeny Frolov. A second Su-37 was similarly converted in 1998.

Su-37 did not reach the production stage, although by mid-2000 Sukhoi introduced several modernizations of Su-27, such as Su-30MKI and 2nd generation Su-35/Su-35BM, which feature similar improvements such as improved avionics and radar systems, and thrust vectoringengines. DesignThe Su-37 is a single-seat, all-weather fighter and ground attack prototype aircraft, derived from the Su-27. The Su-37 includes several updates over the Su-27, including all-weather multi-mode passive electronically scanned array radar with synthetic aperture, terrain avoidance, terrain mapping and a rear-facing radar. The airframe includes a percentage of parts made from composites, unlike the all-metal Su-27. Additionally, the Su-37 incorporates the AL-37FU engines equipped with thrust vectoring. The Su-37’s nozzles are variable in pitch and travel plus or minus 15 degrees, they can be operated differentially to provide a rolling moment.