Great, logical puzzle! ~:) @Margpheb: I think maybe there wasn't enough room for the upper case R. I've had to resort to lower case letters before too when I just can't seem to fit the upper case letters in. :)
Ah, this was a good one! I actually thought the black regions were background right up until the picture was almost done, and I realized it was actually the plane. I suppose it camouflaged itself better than I was expecting. :^)
@Margpheb: I think maybe there wasn't enough room for the upper case R. I've had to resort to lower case letters before too when I just can't seem to fit the upper case letters in. :)