The main reason why altitude sickness does not occur when flying is the air pressure regulation in the aircraft. Aircraft, especially commercial airliners, maintain a relatively stable air pressure environment during flight to ensure the comfort and safety of passengers and crew.

As the aircraft rises, the outside atmospheric pressure gradually decreases. To prevent a sudden drop in pressure in the cabin, the aircraft’s air conditioning system releases compressed air to maintain an internal air pressure close to sea level. This means that even if the aircraft flies to a very high altitude, the air pressure in the cabin will still remain at a relatively comfortable level, usually around 8,000 feet (about 2,440 meters), which is lower than the sea level pressure in the plains, but still above the threshold for altitude sickness (usually above 2,700 meters above sea level), so under normal circumstances, passengers will not experience altitude sickness symptoms due to the decrease in air pressure in the cabin.

In addition, the aircraft is equipped with an oxygen supply system that can provide an additional supply of oxygen when necessary, such as during an emergency descent or flight over extremely high altitudes, ensuring that passengers and crew have enough oxygen to inhale, further reducing the risk of altitude sickness.

Altitude sickness is a series of physiological reactions caused by the body’s exposure to lower atmospheric pressure at high altitudes, resulting in a decrease in the amount of oxygen in the blood. Symptoms may include headache, nausea, vomiting, fatigue, insomnia, loss of appetite, etc. However, since the air pressure inside the aircraft is regulated to be similar to sea level, passengers will not experience this problem on the plane.

Of course, individual passengers may experience discomfort even on board the aircraft due to their personal health or other reasons, but this is not a typical altitude sickness, but a symptom of aviation sickness associated with changes in air pressure, changes in oxygen content, dehydration, etc.

In addition, the process of ascent and descent of the plane is relatively fast, and the human body does not have enough time to adapt to the changes brought about by the high altitude, and the plane has already passed through this altitude area, which is one of the reasons why altitude sickness does not occur when flying.