Is it safe to fly when suffering from clogged ears caused by a cold?

Safe, but painful.. I wouldn't necessarily cancel a flight if you have a cold, but because of the pressure change, you might have some pain in the ear. I recommend to my patients taking some sudafed and Ibuprofen about an hour before the flight, and if it's a long flight, also about an hour before landing. If the pain gets really bad, have a doc check it out after a day or two. Happy flying!