Thanks for the recs!

We stopped bringing the carseat on the plane around 2+. Have a CARES harness, but our DD pretty much refused to use it. So I think you'll be fine with just the plane seatbelt. Since the baby is a lap child, even more reason to skip the carseat since that will give you a bit more space for all of you.

You don't need to bring anything, but I believe you could bring the carseat if you wanted (but check your specific airline regs).

I haven't flown with the two kids yet, and last time the oldest was in an infant car sear in the plane. Can anyone answer if I can/need to bring car seat for the plane for the 3 yr old for a one hour domestic flight? Does she require any harness, etc? 1 yr old is travelling as a lap child.

Thanks!