I'm not sure what your departure times are, but we just completed a trip to Hungary (10:45 minutes to Munich, 3.5 hour layover, 1 hour to Budapest, 4 hour drive to my in-laws' home) with my 21 month old. We scheduled it so that we left LAX at 9:30pm, so the kid was ready for bed. We did not purchase a seat for him, nor rent a bassinett or get seats in that row with extra legroom. He fell asleep about an hour after takeoff and didn't wake up until we landed in munich (save for about 1 hour halfway through where the darkness bored him so we watched cartoons till he feel back asleep). He spent the next 3.5 hours in Munich just running amuck in the airport, with either me or dad running after him. Then he slept again on the flight to Budapest. In Budapest, he was a little disoriented, feeling untired but it's still nighttime. The drive to my in-laws was about 3 hours long, but we stopped 3 times when he got too fidgety for the carseat at reststops so he could run around. We arrived at my in-laws' home about 3am and with all the excitement the baby feel asleep around 5am with the rest of us. We slept until about noon and were basically all reset.
On the way back, we left Budapest at 11am, so I feared he'd be awake most of the trip. THis time, however, the gate attendant changed our seat to give us the bulkhead row and got us a bassinett (for free!). Surprisingly, the baby went down for a nap after about 1.5 hours, and actually slept until about 1.5 hours before landing. Those 3 hours were tough because all he wanted to do was jump around and we couldn't let him. We carried a backpack full of new toys he hadn't seen, but they weren't interested enough for him. We tried videos which lasted him about 10 minutes... it was tough, but like I said, we got super lucky. I hope you do too!
Words of wisdom, carry a small backpack with extra clothes, diapers, drinks, snacks and some toys. We left out the snacks part by accident and he got cranky. As an infant, they don't actually get a meal, so both hubby and I had to share parts of ours, leaving us hungry!
PATIENCE is the biggest component, and also to be self-centered in that you need to focus on your baby's needs, not the distraction or discomfort of others. If your baby cries, oh well. You're never gonna see those strangers again, so don't worry about trying to please them and make THEIR flight comfortable. You'll get stares and even some comments, but don't worry about them, worry about pleasing your kid!