Hmm, I’ll start by mentionning I stopped using Blender for a while and came back to it recently so I forgot some basic stuff so I’ll need a little help.
It is Sift-F to fill it in . But why do you want to do that ? You’ll wind up with ugly geometry you’ll have to deal with later … do you not have side view of the airplane ? It would be better to start with a simple plane or a a cube modified to the overall shape of the plane then to have the airplane’s cross section like that . Or better - since you have the outline just select some edges and start extruding in the side view . This will give you a good idea of where to place the various parts by extruding forwards or backwards depending on the part and then you can scale the nose edge to get it to a point etc .
If you don’t have any side views of your plane you might want to open up the UV window and load one of your diagonal images into it for a on screen referance (I do this myself - as the background image disappears when you rotate your model - even if you have front/side views) .
And when you start extruding you might want to make sure you lock the axis you are extruding i.e. E key then Y key etc. (most likely y axis in your case) . And delete one half of your outline and use the mirror modifier with clipping on (why do all the work when you need to do only half ?)
Hey, I did that earlier. I found that it was easy for me to start with the top view, and then I extruded down to form the body. Just follow the outlines of the blueprints for where to put the verticies, etc. This is how it turned out, if you’re interested.
I thought it was Ctrl+F or Shift+F, but that didnt work. Unless I’m missing something.
Thanks for the advice! and no I dont have a side view of the plane. only diagonal ones.
I found that it was easy for me to start with the top view, and then I extruded down to form the body. Just follow the outlines of the blueprints for where to put the verticies, etc. 
