At 60,000 feet, the windows were warm to the touch. Not from sunlight — from the aircraft itself cooking at 120°C because it was moving too fast for the atmosphere to handle. That was Concorde. Mach 2.04. Cruising speed: 1,350 miles per hour. So high above the Earth that passengers saw the planet curve beneath them. So fast that the aluminium fuselage expanded — stretching up to 10 inches mid-flight — then contracted as it cooled on descent. Engineers didn't just design an aircraft. They designed a machine that breathed. London to New York. Three hours, thirty minutes. You'd take off after lunch, and the sun would chase you backward across the Atlantic. Only 20 were ever built. Only 14 entered service. Only two airlines ever flew them: British Airways and Air France. A round-trip ticket cost $12,000 — about $66,000 today. The cabin held just 100 seats. Champagne, lobster, and the faint vibration of four Rolls-Royce Olympus engines pushing you past the sound barrier while the sky outside dissolved from blue to indigo to near-black. The passenger list was a velvet rope at 55,000 feet. Over 2.5 million people flew supersonically across Concorde's 27-year career. Most of them on just two routes — London and Paris to New York. On July 25, 2000, Air France Flight 4590 was airborne for 90 seconds. All 109 on board killed. Four on the ground. The only fatal accident in Concorde's entire history. Service was suspended, briefly resumed, then retired for good on October 24, 2003. Here's what lingers. Every surface on that aircraft told you something extraordinary was happening. The seat warmed beneath you. The window frame radiated heat into your fingertips. The horizon bent. The atmosphere thinned to nothing. No commercial passenger has touched Mach 2 since. The sky got slower the day Concorde stopped flying.