Merge to center ought to bring the vertices you’ve highlighted into a single vertex, making a nice point, just where you want it. OK: it’s not doing that, but you’re getting “weird results” instead.
It would be helpful to have a screen shot of the unwanted results, since that would eliminate guess work. It I had to guess, though, I’d guess you accidentally extruded twice (you may have a “key bounce” on your keyboard) and have two faces instead of one.
Try pressing ctrl Z to get into wire frame, select “one” vertex, and merge it. If you get a “removed n vertices” message (something other than 0) then that’s the problem. Eliminate doubles should solve that problem, but you may need to increase the eliminate threshold a bit to get them all.
As far as whether you’re going about it the right way, well, there are many ways to do almost anything in Blender. Personally, I’d start with a plane, then merge two of the vertices to get a triangle, then extrude the edge along the fuselage, scaling in or out as I went. Others would stretch a cube into a rectangle the proper length, make additional edges with loop cut (Ctrl+Rkey) and then push verts around to match the background image.