Commercial aviation in-flight emergencies are relatively common, so it is likely that a doctor travelling frequently by air will receive a call for help at some stage in their career. These events are stressful, even for experienced physicians. The present paper reviews what is known about the incidence and types of in-flight emergencies that are likely to be encountered, the international regulations governing medical kits and drugs, and the liability, fitness and indemnity issues facing 'Good Samaritan' medical volunteers. The medical and aviation literature was searched, and information was collated from airlines and other sources regarding medical equipment available on board commercial aircraft. Figures for the incidence of significant in-flight emergencies are approximately 1 per 10-40 000 passengers, with one death occurring per 3-5 million passengers. Medically related diversion of an aircraft following an in-flight emergency may occur in up to 7-13% of cases, but passenger prescreening, online medical advice and on-board medical assistance from volunteers reduce this rate. Medical volunteers may find assisting with an in-flight emergency stressful, but should acknowledge that they play a vital role in successful outcomes. The medico-legal liability risk is extremely small, and various laws and industry indemnity practices offer additional protection to the volunteer. In addition, cabin crew receive training in a number of emergency skills, including automated defibrillation, and are one of several sources of help available to the medical volunteer, who is not expected to work alone.