The Su-27 exists because of the F-15. When the U.S. launched its “FX” heavy-fighter program, the USSR responded with PFI, later split into the heavy Su-27 and the light MiG-29 — a high/low mix mirroring the American F-15/F-16 pairing. But the first T-10 prototype was aerodynamically flawed and cost a test pilot his life in 1978.

Sukhoi made a bold call: instead of refining the T-10, they rebuilt it almost wholesale into the T-10S (1981), with a new wing, outward-canted twin tails and a refined blended lifting body. That gamble produced one of the finest airframes of its era — and the template for a dynasty of Flanker derivatives that Russia and China still build today.

In Pugachev’s Cobra the Su-27 pitches nose-up past vertical to roughly 110–120° angle of attack — momentarily flying tail-first, nose to the sky — then drops back to level flight without losing control or much altitude. It has no direct combat use anyone can reliably name, but it screams control authority and low-speed stability: proof the Soviets had built a genuinely world-class dogfighter. The maneuver became the Flanker’s calling card overnight.

Radar makes a fighter visible the moment it switches on. The Su-27’s infrared search-and-track sensor sidesteps that: it detects the heat of a target and cues a shot without the Flanker ever radiating. Paired with a helmet-mounted sight that lets the pilot cue the off-boresight R-73 wherever he looks, the Su-27 could fight passively and lethally — a combination the early F-15 lacked, and one that made the Flanker dangerous well inside visual range.

Firm figures for the Su-27 are slippery. Sources give maximum takeoff weight anywhere from ~28 to ~30 tonnes depending on how “normal” versus “maximum” loadout is counted; combat radius is variously quoted from ~1,300 to ~1,500 km depending on altitude and profile; and unit cost (~US$30 million) is an approximation with no single authoritative figure, varying by variant, year and export deal. Production totals depend on whether you count only baseline Su-27s (~680+) or fold in two-seat and export subvariants (~800). Treat the round numbers here as good working figures, not settled fact.