you can just completely remove the black space on the top layer in photoshop. But the lighting would still be wrong. The Earth and moon is backlit by the sun while the ships are front lit. You'd have to darken certain part of the ships to make it work and since the sun is directly behind them the angles of the shadows would be different. And it looks like you pasted the ships over and over but the perspective is all over. Even though they're in space they would all still be heading in the same direction so they should all still line up. Finally, if you have bigger versions of thos ships, I' say don't be afraid to break one or two in the foreground. Have them coming in from the left and maybe even have a couple of tiny ones going in behind the earth just to show how big the fleet is.