Thanks Danny

I appreciate you taking the time to look into this.

>Another thing I noticed is that the main curves you have there have a lot of control points,
>was this a result of it being a projected curve ?
Yep, those curves have been projected onto the fuselage of the aircaft and the one on the wing has been generated from wing surfaces edge.

The yellow curve represents the trailing edge of the wing fillet (according to the blueprint reference I am using) but I am beginning to doubt that it is accurate or else you can't get a smooth flowing wing fillet as you have generated. I'll do some more checking of photos of the real aircaft to see if it differs from the blueprints.

Thanks for the tip about extending curves to a surface, I didn't know you could do that, so that is a really good thing to know. I think I would use it a lot.

You've certainly helped me solve this problem on all aircraft that I do which contain wing fillets !