Jen Spain gave some really good ones.
A few more ideas:
Take a couple of changes of clothes onboard for you and him. If my son doesn't throw up on me, he spills cokes and tuna fish on me.
We also tell him "the captain is coming!" whenever we can't get him to do something like wear seatbelt, stop kicking seat in front, etc. Sure enough, a uniformed flight attendant is usually passing by, making it real and he all too quickly obliges. He has no idea what the captain will do, but the uniform is enough to impress!
Walk him up and down the aisles and take him to the service galley where he can charm cheese n crackers, fruit, etc from the flight attendants. On one long haul flight my son ate better than he had in weeks for the sheer novelty of getting food from behind the curtain.
san fran in spring! it'll be great.