The Lockheed SR-71 Blackbird was an American long-range strategic reconnaissance aircraft and the fastest air-breathing crewed jet ever built, cruising above Mach 3. Developed by Lockheed's Skunk Works in the 1960s, it flew spy missions for decades and was never shot down.

The SR-71 could sustain speeds above Mach 3.2 — more than three times the speed of sound, around 3,500 km/h — at altitudes above 25,000 metres. It famously outran missiles by simply accelerating, relying on speed and altitude rather than weapons for survival.

The SR-71 was built by Lockheed's secretive Skunk Works division, led by legendary engineer Clarence "Kelly" Johnson. Constructed largely from titanium to withstand the searing heat of high-speed flight, it was a marvel of Cold War engineering decades ahead of its time.

At Mach 3, friction heats an aircraft's skin to hundreds of degrees, which would weaken aluminium. The SR-71 used titanium alloy to survive these temperatures — ironically, much of the titanium was sourced from the Soviet Union, the very nation it was built to spy on.

No. Despite many missiles being fired at it over hostile territory, no SR-71 was ever lost to enemy action. Its combination of extreme speed and altitude made it nearly untouchable — though rivals tried to match it, as in the story of the Soviet SR-71 that never flew.

Among air-breathing jets, the SR-71 holds the crown, but the rocket-powered North American X-15 flew far faster still, reaching nearly Mach 7. Pure rockets aside, the Blackbird remains the fastest jet-engine aircraft in history.