I flew round trip Australia-New Zealand 3 times before Baby From Mars was 6 months old, so hopefully this will come in handy. I was by myself for 2 of those trips, so if you have an extra pair of hands things should be a lot easier!
See if you can schedule flights around naps - you might be lucky and have them sleep on the plane but this is doubtful, especially as they get a little older. If you get them freshly napped on the plane they can be in a better mood. One bad flight was delayed 4 hours and she was way overdue for bedtime, and was trouble on the flight.
Ask about a bassinette option - my flight gave me this which helped when she was 3-4 months old and she slept - by 6 months she was too aware of what was going on and wouldn’t.
I breastfed on takeoff and landings, and never had any issues with ear popping - if this won’t work for you a dummy can help. ’
I also brought lots of quiet toys to keep her entertained - graphic cards, books, soft toys etc. A few that you can rotate can help keep things fresh.
I carried her through the airport in a sling - it meant no unloading her from a stroller, or having to return this at the gate etc and gives extra hands. I also found she was much more settled (although be aware that they get you to unload them from the sling to seatbelt you both in, so don’t make the mistake I did the first time of getting her to sleep just as we boarded!
Go for walks - it helps calm them down and I do think they can get bored sitting still for a long time. I had stewardesses who offered to carry her too - use this if you need a break.
Bring something you can eat with one hand. Usually not enough room to put a table down and you may need to eat.
Ask when you check in if there’s a chance of a seat away from other people ‘to spare them in case she cries’. This got me a row to myself, which is great if you need to put them down to sit, or eat, or just rearrange things.
Above all, just relax (hard I know). People expect babies to make noise, and they only care if you are clearly not doing anything to try to calm the baby. And if they still don’t forgive you then, stuff them. You can’t do more than you can do!