Medical emergencies sometimes arise in the isolated and confined environment of a commercial aircraft. Because a physician passenger may be on board in 40% to 90% of all commercial flights, it follows that this physician may be asked to render assistance to an acutely ill passenger. Although data suggest that the incidence of such emergencies is low, the potential for serious events necessitates a degree of familiarity with the nature of emergencies in the air and with the options available to the travelling physician.