I just learned something really cool with 3D spline in Onshape! ( I feel like I should have found this out a LONG time ago 😂 )
So if you are making a nose for a plane ( F-16 in this case) and you are using 3D splines for controlling your loft profiles, I would have normally just used "Match curvature at end" (or start) and I would have gotten the curve I wanted.....
but if you flip to the side plane, you might get this funny curve
You can actually control that by using The match curvature at start (Or vise versa) and select a line along the plane that is perpendicular to the one you used for your other curve and then you can control the curve along that angle like this: