So in a jet - at high altitude... Mach number determines Vne...(right?) My problem is that in FSX, if my autopilot is set to mach .82 (which is the max speed on an A321) every once in a while it jumps to overspeed and starts clicking at me. Then I have to turn it back down to .81 and back again if I want to "recalibrate" the bug on the speed tape... In real life, if autopilot is set to Mach mode, does it constantly 'update' the bug on the tape if it were changing? (say during a climb or a descent?)