What could be one result of exceeding critical Mach number?

Explanation

Beyond the critical Mach number, local airflow over the wing goes supersonic and forms shock waves; the FAA handbooks describe the resulting buffet, loss of control effectiveness and Mach tuck, all of which make the aircraft difficult to control. Drag rises sharply rather than decreasing, and a propeller stall is not the consequence of exceeding the airframe's critical Mach number.