Originally Posted by
fr8tmastr
I think many waist $$ when it comes to this. The rules say, "nothing sticking to the aircraft". Its a yes or no answer. There are many out there that will deice just because somebody else did, or because there are a few flurries about. Again yes or no, is the stuff sticking? Will it stick shortly? this requires some thought, IE did the blizzard just start? Granted there are always grey areas that can pop up, if so, spray it. But the majority of the time its really that simple.
It depends upon the ops specs and the airport. Many airlines require Type 1 and 4 if there is any active precip below 0. "nothing sticking to the aircraft" doesn't apply to operations when the FOM overrides it.