Alpha Channels

I'm currently repainting a plane with my own custom livery. I want the lower fuselage to be metallic and shiny, but can't seem to get it to work at all. The bottom of my plane is currently painted a grey, and when I apply an alpha channel (with a charcoalish grey), in game nothing happens.
In DXT is sees the alpha channel so I know it there.
Also when I save in TGA form in Photoshop I have to save in 24bit to save the alpha channel (though in DXT it looks a bit messed up). In bmp I can save in 32bit and the alpha channel is there, but the effect is still the same in game.
Photoshop says TGA's can't be saved with alpha channels (and in the Save As... dialog the Alpha Channel check box is shaded out so I can't choose it, but all the tutorials I come across say to save it in TGA with Alpha. That would be great if Photoshop let me.
I'm I doin' something wrong? Any help would be appreciated...
In DXT is sees the alpha channel so I know it there.
Also when I save in TGA form in Photoshop I have to save in 24bit to save the alpha channel (though in DXT it looks a bit messed up). In bmp I can save in 32bit and the alpha channel is there, but the effect is still the same in game.
Photoshop says TGA's can't be saved with alpha channels (and in the Save As... dialog the Alpha Channel check box is shaded out so I can't choose it, but all the tutorials I come across say to save it in TGA with Alpha. That would be great if Photoshop let me.
I'm I doin' something wrong? Any help would be appreciated...