H.,
I just flew from VT to FL last week and I packed two back packs which I kept under the seats we occupied: one with all the diapers, wipes, dry finger foods & snacks & toiletries that have to be in 3-1 ratio that the TSA requires (http://www.tsa.gov/travelers/airtravel/children/index.shtm) and one full of nothing but new little toys that my 11 month old had never seen before. I put in books, finger puppets, a puzzle, a magna doodle, etc., and that kept her engaged for most of the trip. I also tried to schedule the flight for times when she'd normally be napping anyway so that she'd rest on the plane. And, because I can't keep her still in my lap for five minutes, much less three hours, I purchased a seat for her & took her car seat for her to ride in instead of holding her in my lap. She had a window seat of her own and this was a lifesaver! If you don't have the funds to purchase an extra seat, you can always show up with your carseat in the hopes that there's an empty space on the plane that they'll let you occupy for free upon taking off. If not, you just have them take your seat below on the plane and it'll be waiting for you when you get off and then you'll have to hold your baby instead.
The other thing that made my life a MILLION times easier was this contraption that hooks up to the back of your carseat called the GoGoKids Travelmate. I couldn't have made the trip without it & can't say enough good things about it. It's kind of pricey, but worth every penny. I'd never travel without it. You can probably find one used on ebay or at http://www.gogobabyz.com/products/gogo_kids.html.
Oh, the other thing I did was save her liquid feedings for take off & landing and had a passifier handy if she didn't want to eat to help equalize her ears with the changes in air pressure. That helped a great deal too.
I think the biggest thing that made the trip easiest for her was just being able to be wheeled around in her car seat and then having the car seat be directly put into her seat on the plane. It was comfortable and familiar to her and there were not a lot of transitions for her to make from place to place or person to person. She went right from our home to her car seat and basically stayed put in her car seat until we reached our final destination. There was no need to bring a stroller or pull her in and out of anything constantly, which can really wear on some babies. Our flight was three hours long and she slept some, snacked some, played a little and I sang to her and played games with her. The other thing I did was pull out new, unfamiliar toys sporadically throughout the trip there and back, so things were more engaging for her. I didn't show her all the toys right away, nor did I show them to her back to back if she wasn't interested in one, that way I had something new to give her if a meltdown ensued (which thankfully, DID NOT!).
Good luck!
R. J.