perhaps this child was one of the violent types, which cannot be controlled without a huge effort. I have a few classmates who worked with autistic children, and the behavior of the kids depends on the severity of the autism...one child can be coherent and friendly and brilliant and the other could be aloof combative and unable to calm down. My class instructor's son is autistic but very mildly so, and even SHE says she would remove her child from the situation herself....its what happens with children of that disability...they need to be removed from the situation and calmed down...thus the airline was sort of in the right. These violent types can be as strong as teenagers when very young, and as strong as men when they are teenagers...I have heard stories of them injuring people by flailing about, and chipping the teeth of a person next to them when they got hit in the face with a fist....and this was a five year old hitting that hard!