Hi L.,
I found myself in a similiar situation. My daughter was 11 months for her first flight. We flew from Philly to Punta Cana just over 3 hours. My doctor recomended Tylenol since she was under 1. I had every intention of giving it to her, however due to hightened security, my Tylenol was confiscated (no liquids were allowed on the plane). No worries though, she was fine. I gave her a bottle when we were preparing to take off, she didn't even cry. As we started to descend, I tried giving her her binky, but she was fussy and didn't want it (Imagine that! LOL!). I quickly gave her fruit puffs, and cherrios, and juice, and she whined just a little, but other then that she did great. Like other Moms stated, make sure you bring plenty of toys to occupy him with, and you should be fine. Also, just a quick note, we opted not to bring the car seat, my daughter laid down for a good portion of the trip, used my legs as a foot rest, and my husbands leg as a pillow, it was great, the pull down tray acted as an activity center. My bother-in-law and sister-in-law went on the trip with us, with their 26 month old, they brought her car seat with them, my neice was not as happy in the seat, she wanted to be held, as this was also her first flight, and she was a little scared, and then lugging it around the airports was more trouble then it was worth. My sister-in-law told me, if she had it to do again, she wouldn't bring the carseat, it wasn't worth it. Good Luck!
L.