hey! that's really good, the lighting is nice.
one thing though, p40's didn't fight 109e's over the pacific
a few points...
your edges are still jagged and blocky. you need to use a softer eraser brush if you're erasing it all, it will make the edges look cleaner. try to get a nice straight line instead of a staircase
if you have a fairly newish PC (one that isn't over 2 years old, and can get a decent frame rate in game) download the high res package from the downloads section of this site. once installed, the plane textures will be much better looking, right now they're quite messy.
props. once you've got all that down, try putting some props on the planes. take a screenie of the plane front on from external view, with the engine off on the runway. cut the prop blades out, select a circle around them, and use radial blur. then resize this prop layer so that it fits on the plane. if needs be, you should adjust the perspective to make it look right. clean it all up with the eraser after you're done
that is a very good shot though, the lighting works great because the clours blend well. good job!