What ear conditions might prevent me from flying? Why do my ears hurt so much during decent?

A common cold could be a concern. Congestion can impair function of the Eustachian tubes, which extend from the middle ear to the back of the nose. The Eustachian tubes are normally closed but can open to allow small amounts of air into the middle ear to equalize pressure, a sensation you may recognize as a popping sound when losing elevation on a mountain road or descending in an airplane. If congestion from a cold or other respiratory infection prevents the Eustachian tubes from properly equalizing the middle ear, eardrum perforations, trauma to the middle ear, and severe pain could develop. If at all possible, do not fly if you have a cold. If you must fly, prepare by taking an oral decongestant and using nasal decongestant sprays which might help improve Eustachian tube function and reduce pain from pressure in the middle ear.