I am wondering how much of a problem aircraft icing is. I realize that ice forming on the wings or other parts of the aircraft is very dangerous but are there some good stat about how many accidents this causes? Is it something that has become fairly simple to avoid? I know there is still some active research in this field but what are their main focuses? I have read a little bit about it and it seems like we know that ice can severely effect an aircraft but to me it seems like it would be easy to avoid situations in which ice could be problem, and why don't they just use something on the wings like the defrosters on the rear windshields of cars.