The T-4 experimental supersonic aircraft, also known as the "Su-100" or "Project 100", first flew in August of 1972, eight years after the United States' XB-70 Valkyrie, which it is said to imitate. The T-4 was made largely from titanium and stainless steel. It featured possibly the first fly-by-wire control system, with a backup mechanical system.

Although it lacked the XB-70's ability to raise and lower its wingtips, the T-4 did have a lowerable nose section, similar to Concorde, to provide better visibility from the flight deck during takeoff and landing. With the nose raised, a periscope was used for forward vision.

A static test aircraft (serial '100S') and a prototype, serial '101', were built. Two further prototypes, '102' and '103', were under construction but not completed. The test pilot for the first flight was Vladimir Ilyushin, son of aircraft designer, S.V. Ilyushin.

The T-4 weighed about 225,000 pounds and was powered by four Kolesov RD36-41 engines of 16,000kg (35,274 lb) thrust with afterburners. It was designed to fly at Mach 3, but is believed to have reached Mach 1.3 or 1.4.

Serial '101' only made ten flights, of less than eleven hours total duration, before the program was cancelled in 1974 or 1975 and the uncompleted prototypes were scrapped. It was considered an expensive under-performer, with continuing problems with its 'fly-by-wire' system. The prototype, '101', remained extant in Russia's Monino Air Force Museum.