Because the Concorde traveled at supersonic speeds (Mach 2.0), it faced intense kinetic heating caused by air friction against its skin. At its standard cruise speed, the temperature of the aircraft's outer skin reached approximately 127°C (261°F) at the nose and dropped to about 91°C (196°F) at the tail. If the plane pushed to its maximum rated speed of Mach 2.2, the nose temperature could spike as high as 153°C (307°F). This heat was so extreme that the airframe actually expanded by about 7 inches (18 cm) during flight. To manage this, the Concorde used a specialized high-reflectivity white paint to radiate heat away and was constructed from a unique aluminum alloy called AU2GN. For passengers, the cabin walls were notably warm to the touch, and the cockpit windows were thick enough to withstand these high thermal loads. This "supersonic heat" is a fascinating piece of aviation history, highlighting the engineering hurdles overcome to fly faster than the speed of sound.