From what I read, it was a female pilot in command and male co-pilot. Physical altercation is never acceptable in a work environment (if anywhere at all, except maybe the gym to vent some steam :P)
It will be interesting to find out if it was a "lovers quarrel", or if the male co-pilot wanted to show her who was the "boss"
Or just plain unprofessional/illegal behavior (assuming it is illegal to physical strike someone).