The Cirrus stall-crash has resulted in related discussions about the relative safety of steep bank angles while descending. Paul says step bank angles can be made with relative impunity from stalls if descending. With due respect I join the dissenting side.
In November 1945, a British jet fighter the Gloster Meteor set a new official world speed record of 606.25 mph. It was two years later before the sound barrier was broken by an American aircraft the Bell X-1. Test pilot 'Chuck' Yeager named the aircraft 'Glamorous Glennis' after his wife.
An approximate formula for the speed of sound through air in standard atmospheric conditions is: Speed of Sound = 331.45 m/s + 0.6 m/s * Deg C. This corresponds to approximately 1100 feet per second, or 750 miles per hour.