Why So Many?

I'm doing a repaint of an aircraft, and every texture has 4 different copies of itself but with differnt letters attached to the file name. This is the first time I've seen this and wondered if it is nessasary to paint each one or if the sim is only needing one of each. It is a FS2002 model, but everything appears to work just fine in FS9.
Here is a shot of the texture folder:

Thanks for any help.
Here is a shot of the texture folder:

Thanks for any help.
