Hello zan29 and Friends
The one shown by Pilou, is Ok ,
but I believe that creating a Network, instead of
a Loft is better-
Cutting the curve into four parts instead of
two I have the edges to create the Network ,
that as a surface, respects better
the trend of the profile-
The file and a fairly explanatory image
at this link :
http://www.mediafire.com/file/kf25s3x6j6bmtt5/Loft-Network.zip/file
Have a nice day to all
al

Yep so an easy way is trim the original curve by drawing 4 Points "On" anywhere you want acording the complexity of the curve!
Use the Browser / Curves for select only curves (4) and then run your Network function! :)
(here + extrude & fillet)



with your curve

Both of those methods have some potentially undesirable surface qualities though. The blend one has 2 singularities, meaning that 2 of the surface's 4 natural edges are compressed down to a single point. That is not automatically an error and is normal for things like a sphere or a cone but on freeform surfaces there is an increased chance of surface distortions in those areas.

The network one does not have any singularities but it instead has indistinct corners where the surface normal will not be well defined because the surface tangents are pointing directly opposite each other. It's also easy for the surface to be self intersecting in those areas as described here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=1127.4
http://moi3d.com/forum/index.php?webtag=MOI&msg=551.4

Whether those issues will be an actual problem depends on what you will be doing with the surface though, in many cases it will be ok.

But to get a "best practices" high quality surface for something like that it's better for it to be trimmed from a larger surface rather than trying to build a surface that has that outline as its own natural edges. So that's why I'd recommend generating something like that as a result of an intersection instead of generating the 3D non-planar curve first and trying to surface the curve.

It looks like it might be intended to have the shape of an ellipse in the Front view, so probably you'd want to have an extruded ellipse to start with and then have something that cuts the end off of that.

- Michael