Feb 9, 2020 -- 6:10PM, lybertyne wrote:
825mph is well over Mach 1 so technically it was supersonic.
Mach numbers relate to air speed and not ground speed.
When commercial aeroplanes get (really) close to going supersonic, it triggers an awful lot of paperwork and necessitates a load of checks, which are both expensive and very definitely frowned upon by airlines!