Originally Posted by
michelda
I think Airbus knows that at FL 390 is not possible to fly at 292 kt…?
You could do a straight 'unloaded' dive at FL390 at 292kt (like they do during manufacturer's test flights), and you'd be doing
Mach 1 exactly. This won't break anything unless you put any significant load on (like a rapid yank to get your nose up), but I imagine the buffet is quite strong. Any load on the wings and you wouldn't technically be 'flying' at that speed of course, just high speed stalling
When they did the flight diving test on the 777-300 the T33 chase plane clocked them at
1.01M. Not sure of the altitude at which it happened.