Who requires a medical clearance to fly?

Fit to fly. Medical clearance to fly is required if: •fitness to travel is in doubt as a result of recent illness, hospitalization, injury or surgery. •you have an existing unstable medical condition. •special services such as oxygen or the use of medical equipment on board is needed. •you are travelling for medical reasons or treatment. If unsure please contact your airline and physician before travelling.
Certain conditions. Some patients may be at higher risk to fly on an airline. Prolonged immobilization during flight may cause venous thrombosis in individuals with preexisting thrombotic or venous disease. Jet aircraft are not pressurized to sea level. For patients with impaired cardiopulmonary function or other health problems (eg, sickle cell disease), supplemental oxygen may be needed.
Any 1 can fly. I don't know of anyone who needs med clearance 2 fly. There r some people who's mds have recommended they not fly 4 various reasons medical & psychological .