I realize this thread is old as dirt, but I actually have the samer qustion.
I've been reading Steven Frowine's
Miniature Orchids, which mentions Aerangis luteo-alba var. rhodosticta; an Aerangis luteo-alba, with all white flowers with a white column; and Aerangis somasticta, which is a species hybrid. Rhodosticta is obviously easy to find; Google brings up info on the somasticta; but I can't find any mention of the all-white version.
Is it not commercially available? Why is the book the only place (besides here) I've even heard about it? (Is the book wrong?)
Maybe this has something to do with the process of wild orchid "domestication"...
Inquiring minds want to know.