The LagrangePolynomialApproximation algorithm used to smooth point-to-point paths, is a really good addition, but it's not done. I have stared at a lot of Interpolated flight paths in the past few days, fighter jets and passenger jets.
The demo in the Sandcastle illustrates how aircraft flight paths can be smoothed to show a more realistic path:
It's true, I believe the LagrangePolynomialApproximation path is better than straight line segments, however the resulting path often arcs-out *prior* to rounding a point, the way a runner rounds 2nd base on their way to 3rd. An aircraft does not do this, it just turns (most of the time).
Don't get me wrong, I could not do better, but I would advise some kind of "aircraft behavior" modification to the algorithm. That an aircraft does not get ready to turn at a point (like runner rounding bases) and that the aircraft is going forward. That an aircraft travel curve going forward is different than the curve going back.
Does this make sense? I hope this is constructive and does not offend anybody. Good job so far.