Hi, JonnY,
It’s a well-known fact that the true speed of your ship depends upon the frame rate that your computer is delivering.
If your frame rate is close to 30 FPS and the speed is indicated on the HUD as 30 kt, your ship will take 2 minutes to cover one nautical mile. If your frame rate is only 10 FPS, it may take about 6 minutes to cover one nautical mile. The true speed will be only 10 kt.
This is because speed and distance traveled is calculated once each frame based on the assumption that the time interval was about 1/30 second.
Because the different players on MP may be getting different frame rates, their ships travel at different true speeds even though they may indicate the same speed.
Regards,
Marty