The drag divergence Mach number, also known as the force divergence Mach number, is the Mach number where drag waves start to form. The drag divergence Mach number is typically between 5 to 10 percents greater than the critical Mach number.
The maximum operating limit Mach number(Mmo) is the mach number beyond which aircraft start to suffer compressibility effects and flutters at high altitude. It's basically the high altitude version of Vne(Vmo).
My question is: what are the two Mach numbers' relationships? Is Mmo always higher than the drag divergence number? If so, how much? Or is it safe to assume that they are more or less the same?