Flying on an airplane can be dangerous or risky for some people with certain physical conditions or ailments, but these same ailments (plus some others) also can pose a danger to healthy people flying on the same plane. So if you're sick, consider postponing your flight, not just because it could be harmful to you, but also because it could be harmful to others.
Pneumonia is a serious and potentially fatal lung infection. It often starts with a simple cold virus that causes mucous buildup in your lungs, but you can also get pneumonia from bacteria or fungi. It is important for doctors to know what kind of pneumonia you have so that they can choose the right drugs to treat it. A bad cough is a characteristic accompaniment to the infection, as is fever, chills and shortness of breath. Not all coughs are part of pneumonia, but when they are, treatment is necessary. Antibiotics are the most common method of treating pneumonia, and doctors often advise patients to stay home, rest and drink lots pf water. People often feel better after taking medication for two or three days, but it can take weeks or months to fully recover from pneumonia.
Medical professionals recommend putting air travel on hold when a patient is suffering from certain illnesses because the changes in air pressure in the cabin and the resulting reduced oxygen levels can create serious consequences. These illnesses include ear infections, bone fractures, COPD, angina and pneumonia, in some cases. The Aerospace Medical Association recommends that people diagnosed with pneumonia, tuberculosis or other pulmonary infections not fly until they are well enough to handle the stress and are sufficiently advanced in recovery that they cannot infect other passengers.
Pneumonia can be contagious under certain circumstances such as viral pneumonia, which is not helped by antibiotics and simply has to run its course. Bacterial pneumonia that is being treated with antibiotics is generally not contagious, but it can be before medication is started. Other non-bacterial and non-viral forms can be contagious as well. The germs spread by sick people usually do not cause others to get pneumonia; rather, the germs would likely infect others with an upper respiratory infection.
U.S. airlines are allowed to remove anyone from a flight deemed too sick to travel, but no specific guidelines exists on what constitutes "too sick." In fact, some airlines will charge you a hefty penalty for choosing not to fly for reasons of sickness. Some others might waive the fee with a doctor's note, and some don't charge a fee at all. It's best to check your airline's policies ahead of time, but not too far ahead, because they can change on a moment's notice.