You have gotten soo much great advice I just wanted to repeat the part about preparing your child. I thought I had when I took my twins on their first flight and thankfully I don't think this is an issue anymore because I don't think they make children do this anymore but.....we had complete meltdown when my son (age 4) had to take his shoes off to go through security. Seriously, I think the poor thing thought he would never see his shoes again, it was very bad. I thought I had prepared them for the experience but the shoe thing had just started when we were traveling and I had never experienced it either so I didn't know. The way home was a breeze because he knew what to expect, soooo much of their world is about expectations and I totally know that, am usually great at it but I got a F for failure in a big way for the shoe thing.
We flew Jet Blue for the sole intention of the televisions. Like others have mentioned, we didn't do much screen time at that age so being able to sit for 3+ hours with a screen was total bliss. The flight was a breeze. My son really loved watching the channel where he could see the direction the plane was going and the speed/altitude etc. One time he was soo excited he yelled out "mommy, we're going the right way" and literally it felt like the entire plane laughed out loud. Once we were able to unbuckle and start to leave the plane I could see people trying to get a glimpse at him, you know the kid who was soo excited to be going the right away. Anyway, the screen was all we needed for the entire flight for my children because they were soo enthralled with not having any interruptions for hours of straight viewing. I had plenty of other things to pass the time but never needed anything (except the lollipops and covered water bottles to help with ears).