On an airplane, people sit in a confined space for extended periods of time, which increases the risk of transmission of airborne infections.
During the severe acute respiratory syndrome (SARS) epidemic of 2003, awareness of the possibility of acquisition of infection on a commercial aircraft reached its zenith when on one flight from Hong Kong to Beijing, 16 of 120 people on the flight developed proven SARS from a single index case.
Deep vein thrombosis (DVT) is the third most common vascular disease next to stroke and heart attack.
[9] Flying 12 km (39,000 ft) high, passengers and crews of jet airliners are exposed to at least 10 times the cosmic ray dose that people at sea level receive.
In low risk pregnancies, most health care providers approve flying until about 36 weeks of gestational age.