The Air Florida accident was caused by more than just wing contamination (definitely not fluffy white snow). They had EPR probe contamination as well resulting in a heavily reduced thrust takeoff. They had almost no experience or training in operating in icing conditions. Dry snow contamination is an allowed contaminant in Cnada at least. Have to verify that there is nothing underneath. FAA did allow frost accumulation on the top of the 737 wing for a very short period of time. Not sure if that was a paperwork mistake, however it was rescinded fairly quickly.