Why did my Litchi mission run so much slower than planned mission?

[pogopilot]

I have flown countless Litchi missions on my old P4 but today I planned a simple out and back for my Mavic Pro that was just about two miles long. I set the default cruising speed to 20 mph. That means it should have taken about 6 minutes. However as I completed the mission layout in Mission Planner, it showed that the mission would take about 8 minutes. Fast forward to downloading the mission to my nvidia and actually running it and it took just over 10 minutes and flew about 5 to 8 mph between each WP! Now there was no great wind . Any ideas why the mission flew so much slower that the way I had set it up?

 

[sonof40]

Metric vs Imperial?