For some reason, certain ZIP/RAR type utilities seem to think that the replacement .AIR file is an installer, which it isn't.  You just copy this file that appears to be an installer into the aircraft folder, and let it overwrite the existing file.   I was confused by this same issue at first.

I have really been having fun learning more about prototypical operation of this bird thanks to these mods.  It's neat when everything happens more or less like it would in real life.