Τhoracic Surgery Department, Athens Chest Hospital (Sotiria), Athens According to the law of Boyle-Mariotte the gas volume of the human body cavities increases when the barometric pressure decreases. The same happens with the oxygen concentration as we mount from the sea level. Both factors affect mainly the patients with respiratory insufficiency. Nowadays, it is obvious that the number of medical air transportations is increasing due to the special geography of Greece, namely the existence of the islands. It is imperative to study all the guidelines for the safety of air transportations taking into consideration the cabinet pressure decreases of many airplanes. The principles and the kinds of medical air transportations are described. The indications of the medical air transportations are set and medical instructions are mentioned, while, relevant conclusions are drawn. Pneumon 2005, 18(2):163-173.