First of all, heart disease patients with severe symptoms or serious arrhythmias cannot fly, as well as patients after heart surgery, especially within three weeks after surgery is also not suitable for air travel. Secondly, cerebrovascular diseases such as cranial injury is more serious, the patient has coma and respiratory rhythm arrhythmia, etc. is not suitable for flying, and the acute period after brain hemorrhage at least three weeks before flying. Then, upper gastrointestinal bleeding, such as acute gastrointestinal bleeding, also can not fly, appendicitis patients are also not suitable for flying, the aircraft will make the gastrointestinal tract of the human body after takeoff by air pressure, resulting in re-bleeding. Once again, patients with severe anemia due to the reduced ability of the blood to carry oxygen, high air partial pressure of oxygen during the plane will lead to dizziness and other patients. Finally, upper respiratory tract infections or nasal diseases are not suitable for air travel, mainly due to the impact of air pressure resulting in insufficient oxygen absorption.