Here are some numbers. A few days ago above Paris at FL400 our Vma was 206 kts and Vmo was the equivalent of 249 kts. Had we been heavier the Vma would have been greater and higher the Vmo would have been less. At sea level, the values would have been 140 or so and 320. For us, the change between Mach and Vno typically occurs just below FL290. Given enough poke you can get to where Vma is greater than Vmo. Possibly interesting to go there but without passengers and a good supply of clean underpants.