Aviation physiology deals with the physiological challenges encountered by pilots and passengers when subjected to the environment and stresses of flight.

Human physiology is evolutionarily adapted to be efficient up to about 12,000 feet above sea level (the limit of the physiological efficiency zone). Outside of this zone, physiological compensatory mechanisms may not be able to cope with the stresses of altitude.

Military pilots undergo a series of exercises in high altitude simulating hypobaric (low pressure) chambers to simulate the early stages of hypoxia (oxygen depletion in the body). The tests provide evidence of the rapid deterioration of motor skills and critical thinking ability when pilots undertake flight above 10,000 feet above sea level without the use of supplemental oxygen. Hypoxia can also lead to hyperventilation as the body attempts to increase breathing rates.

Altitude-induced decompression sickness is another common side effect of high altitude exposure in unpressurized...