[rattlsnak]

As far as visibility, I fly a 757 and do Cat III autoland ops quite frequently on the east coast in the winter..(and occasionally when fog banks move in at places like LAX, SEA, PDX etc. We can go down to 500ft. RVR for T/O at most airports. As far as icing, the engine anti ice comes on anytime you are in visible moisture and the temp is below 10C. Wings usually only come on when we see ice sticking to the airframe somewhere which is in fact, really rare. Most bigger jet transport airplanes don't have a pilot selectable continuous ignition source to turn on.