L.S.
If he's comfortable in his car seat, buy a ticket for your son, or pick flights that are not popular and have empty seats. If he hates the carseat, or you don't want to spend the $ for a seat, wear him with a carrier & he'll be cozier & you'll have your hands free.
Bring a medium size lightweight blanket that you can use on the plane to cuddle, AND use in the airport during your layover. Airport floors are gross, but he'll enjoy the chance to stretch out & play a little, especially after being cooped up in the plane.
Bring infant Motrin or tylenol on the flight for the teething, or in case of emergency earaches at your destination. Bring lots of bottles or be ready to breast feed a lot - milk is the best soother for ears popping, or restlessness on the plane.
Check whether your airplane has a changing table - your itinerary will tell you what kind of plane you're on, and you can check seatguru.com for whether the plane has a changing table. (Boeing 757s don't, Airbus 319s do, etc.). If it doesn't, plan to bring extra hand sanitizer, and something to lay down in the galley, or on an empty seat, or god forbid - the toilet seat in the lav, etc. to do a change.
Make small mini diaper changing "kits" with 1 diaper, some wipes & a onesie. You won't want to lug your whole diaper bag to the lavatory, if you could just take a little quart ziplock with your essentials.
Plan to check your bags. Try to limit the amount of stuff you carry on. You NEED: 2 extra 1-pc jammies for your son, 3-4 mini diaper kits, an extra shirt for you (in case of blowout incidents), bottles, small snacks (if he's on solids), a few critical toys (At 6 months, we always traveled with a book, something to shake, something that lit up, something to cuddle, and something to suck), a bottle of water and snack for you, your essentials (wallet, keys, lipstick, etc.) and a magazine for you. Nearly everything else is a hassle. Make sure you can justify anything else you bring onboard.
When you get to your seat, put all of your essentials in the seatback pocket, so you have bottle, pacifier, diaper changing kit, a toy, book immediately at arm's reach.
Keep in mind: your priorities are first to your & your child's safety, then your comfort; lastly, the experience of those around you. If you have a rough time, because of the teething, or whatever happens on your first trip with baby, know that the plane ride WILL END, and if other passengers give you a hard time, you'll likely never see them again. Another poster thought that is not good to say - I don't mean you should disregard your fellow passengers, but I do mean that you have to keep your responsibilities in perspective. I don't mean to invite bad karma or anything by allowing your son to scream uncontrolled on the plane. What I mean is that, sometimes, there just isn't anything you can do- once you try bottle, changing, toys, a book, a new outfit, a walk in the galley of the plan, etc, you're out of options. You're stuck on a plane. You can apologize to the folks around you, but you sometimes just have to take a deep breath and know that it will end once you land, and it will be OK.