I've never done a plane sprite before either, so I had a stab at it.
I don't know if this will be helpful because I'm still learning and it ended up not looking like yours at all, but I thought maybe I'd share the process I went through.



1. First I used Google to find some pictures and 3-view plan of my plane. I chose a P-51D Mustang, because there are lots of images and I like its shape. I got a top view and scaled it down to roughly the size I wanted.
2. Blocked out the plane.
3. Tried adding colors and detail things to make it look more plane-like.
4. Tweaked the shape and colors until I was sort of happy with it. I used ptoing's C64 palette because I was in a retro sort of mood.
5. Roll the plane to one side, using reference images. I still don't know if I like it, but I guess it will do.

Then I some in-betweens and animated it:
Hope this helps Keep pixelling!