I have flown with my children at all different ages and sometimes by myself. Here are some of the things I have found to work:
1) If he is mobile, waiting at the airport is the time to let him be that way. It is too long to expect him to sit still at the airport AND on the airplane.
2) Bring his lovey if he has one...a blanket, special toy, binky, etc.
3) Bring a variety of toys to keep him busy but don't let him see them all at once. That way, when you bring one out you will have the "new and wow" factor. :)
3) Bring snacks, meals, and drinks unless you are nursing. Get him to drink (or eat as a second option) during take off and landing but remember that the ascent as well as the decent lasts for longer than just getting the wheels off and onto the runway. If he gets very upset and you start to think he might be having trouble with his ears, ask for a very warm, wet towel and hold it behind his ears. You'd be surprised how much it can help.
4) Make sure to pack plenty of diapers and accessories (wipes, ointment, etc.) and a change or two of clothes. I would change him a bit before boarding so he is starting with a fresh bottom.
5) There is always the suggestion of bringing a portable DVD player and some Baby Einstein videos if it is going to be a long flight. :)
6) Relax and have fun! Obviously you want to keep him comfortable and happy but if he does start crying, don't stress because you are worried about what the other travelers are thinking. He is just going to pick up on your stress and get even more upset. He'll be ok! :)
7) If you DO nurse, don't forget the pump. You never know and it's better in my opinion to have it and not need it than the other way around.
8) If you want to bring a stroller, I highly suggest getting a lightweight one like a Combi. They fold up into thirds so they are VERY compact but they are MUCH more supportive and safer than an umbrella stroller. That one even has a shoulder strap. Personally I think those umbrella strollers should be outlawed and cringe every time I see a baby that can't sit up in one of them or see one start to tip over which I have seen way too many times.
Enjoy your trip and I hope my suggestions have helped!