It happens when there is not night-texture for a particular area of the plane. That is the easier problem. On older 3D models, the Alpha cahnnel means not reflectivity, but transparancity. This way, if you have a night texture with alpha channel, it may look transparent...
If you have a night texture missing, here is the easy solution:
Night texture filenames are usually the same as the day ones, only the extension is different. Usually day textures filename end with "_t.bmp" or "_T.bmp", while the night textures end with "_l.bmp" or "_L.bmp". If you have a night texture missing, then simply paint a 256x256 sized black BMP image, and save to the desired name + the "_L.bmp" extension.
Please report here, if you have the same problem at ANY of the EHM fleet. Thank you, although all the textures were tested last year, so...
