Manflex55
Without wishing to sound too harsh, I'd say that you have no (let alone a basic) knowledge of aerodynamics.
Aircraft regularly exceed MMO without breaking up and/or falling out of the sky.
MMO is a factored figure that provides a safety margin to protect the first part of the entire airplane from exceeding the "local speed of sound".
To generalise, with modern "airliners" the most usual limiting factor is not the airframe but the airflow through the engines.
If MMO was the "break up" figure then all UK Boeing 757's would have crashed.
Why?
The FAA certify the airframe to MMO 0.86 but the CAA to 0.84, for what ever reason.
So, day one I fly B757 airframe number 123 at M.85 as a "G" registered airplane. Day two I fly at M.85 and it's now "N" registered. Why didn't I crash on day one?