Iu2019m assuming that the child is flying either alone or with one of the parent. In Canada it is necessary to have a notarized consent letter along with a Statutory Declaration commissioned along with that letter. However, as a precaution, I would suggest that you call the immigration or the Consulate of the respective countries to understand the rules when travelling with one parent or an unaccompanied minor. Each countries holds its own immigration policies and its always best to find out beforehand and I would not base it on my answer as the correct advice.