Speed settings indeed . . .
Back down on your Overclock for CPU and RAM and also if you're clocking the GFX back that to stock too.
I was scratching my head wondering what was going on.
I'd tried every interval thinking all of the sudden I moves a setting because it had always worked great then one day as if out of the blue, The planes I was trying to fly formation with would stutter the whole flight.
What had happened was I overclocked my CPU and RAM, I guess maybe too much but I had forgotten I did it,between the time I clocked her and the next time I decided to fly.
I had tried everything else, I figured let me just bring it back to stock speeds.
It's back to smooth running while recording myself and flying along side myself.
I know this will help someone even though the O/P is quite old
I came here looking for answers about 3 weeks ago.