About the colds, i've experienced that too. Landing in Chicago, absolutely horrible I know the pain! But I read somewhere in a book that it has something to do with your eustrashion tubes near your ears being clogged with the pressure changes, which creates head splitting pain. You need to make sure you keep your jaw moving.. by making weird faces in flight, or by chewing gum. Because I did not have gum when we were landing and I've never flown without gum since, I had chronic ear problems when I was younger. Fresh air is circulated through the cabin every 5 minutes or so, so you're not sitting in the same air the whole flight.
My experience happened in December, I was flying from SLC
on Delta. It was gorgeous outside until we started getting near Anchorage, the clouds turned like really dark grey. It started out as a light chop, the seat belt signs came on. Then, the plane all of a sudden sways and slams down hard.. and starts dropping. After that the pilot came on and was like 'FLIGHT ATTENDANTS NEED TO
IMMEDIATELY GET TO
THEIR SEATS, AND
ANYONE WHO IS
A SEAT NEEDS TO
FIND THE NEAREST ONE AND
'. Then we level off and we hit an extremely severe chop.. I was right behind the wing.. the wing is bouncing up and down and it's starting to freak me out that a wing can bend that far. So the second time, the plane started shuttering and slammed down again... this time bins opened, and the wing tips were vibrating.. people now were cussing, and I was freaked out. So we had like an hour and a half left in the flight and the seatbelt signs were on the rest of the time.
So we started our descent into Anchorage.. and we're flying out over water and the plane is.. slamming down still not as bad but we're steadily dropping.. and the lady behind me is like literally hyperventilating.. and was blaming Delta for putting her through this experience. I was really shaken up I felt really weak when I stood up to get off.
The second time would be after takeoff in a 763 from SLC
last summer, and the plane started dropping after take off, kind of freaky but then again.. it happens lol I'm still here and alive.