Last winter I saw many European 747s taking off from a Northeast US airport with the first half of the runway "half inch snow/ice" and the last half of the runway contaminated with "3" packed snow and ice." We waited 3 hours for the airport authorities to clear the runway, but the Euro 747s took off one after another. They were heavy and had V1s and Vr well into the contaminated portion. Abort??? No way. They'd have been in the water. I couldn't believe what I was seeing.