UT2 AI Aircraft and Mipmaps

I was reading the Software and Hardware Guide for FSX by Paul Johnson and he mentions that:

"Any time the GPU receives a texture – which, of course, it’s doing constantly – it expects to see an alpha texture. If it doesn’t find one - it looks for one: if there are enough textures without alpha’s – it will cause stuttering and/or hesitations. Similarly with MipMaps..."

So of course I ran AphaSearcher and found that almost all of the UT2 aircraft are missing Mipmaps. AI traffic is hard enough on the system as it is, shouldn't these have mipmaps in them or maybe there is a reason they don't?