Aviation is the most commonly used mode of international travel, and is becoming more popular.

All forms of flying demonstrate extreme physiology models in the human subject; in commercial flights the passengers exist in a hypoxic and hypobaric environment, and even previously healthy individuals are at increased risks of harm from conditions such as venous thrombosis and disturbed sleep patterns.

Agile aircraft, as used by the military, offer even more extreme challenges to human physiology. Future research will allow all forms of aviation to become safer at a time when the number of people flying continues to rise dramatically.