An important aspect of globalization and modern economy is the fact that patients with acute or chronic disorders, after previous accidents or surgical procedures want or have to travel by air. When assessing the fitness to fly, the physiological conditions on board commercial aeroplanes, e.g. hypobaric hypoxia and pressure induced volume changes of trapped gases, limited diagnostic and therapeutic possibilities, specific aspects of the prevailing disease and the individual patient have to be taken into account. This paper discusses the most important aeromedical criteria and provides a quick and comprehensive table of reference for the assessment of the fitness to fly for the most important and common medical conditions.