When a medical emergency occurs during a flight operated by a commercial airline, the assistance of a physician-passenger fortuitously present aboard may be requested. This physician becomes bound by both his professional and civil responsibilities. However, in the case of a serious problem, he would usually ignore the question of the jurisprudence of the country where the emergency occurs. In discussing this issue, this paper analyses different situations and risks that the physician may incur and points out various defects in the law not currently covered by existing international conventions.